They need to match the finish and be provided by whomever provides the doors. That will not be cheap. Dont forget scribe moldings, toe kick, and all of the rest of the required moldings needed for a professional install. All of that has to come from the same source as the door provider or it will not match. Always buy an extra stick of every molding. You don’t want to be waiting 6 weeks for it to show up and have to pay UPS freight too. And then not match. Yes, it’s more expensive up front. It’s what needs to happen.

Moldings, fillers, and end panels, back panels, and other required cover panels panels can add up substantially, but it is not a place to skimp. It can be 1/3 the cost of the whole order. And this is one thing IKEA effect people forget to mention or account for. And it’s something newbies don’t know how to account for in both designing and ordering either. Especially when doing 3rd party. All of that has to be ordered at once, from the same source.

There's nothing magic about it, it's just wood.

Find a good local lumber yard (not a big box).
Buying extra is a good idea.

“Just wood” that has to match the door finish, or it ruins a design. If painted, “just custom cut MDF” will be the much better choice. (Table saw skills required for any of this, including IKEA.) MDF is what IKEA uses as standard. Wood will show the grain through the finish, or delaminate.

If you have to ask this question then you are not really ready to build your own kitchen. You wouldn't use veneered plywood for a painted finish and if you did it would have to be sized correctly and banded before finishing. Doors and drawer fronts have to be drilled correctly or everything will be difficult line up. As for a local shop the does a CV finish don't assume just anyone does this and if they are good it won't be cheap.

The doors, whether i do them or I get them from Barker will be poplar frames with MDF panels (shaker style). So i was going to use a poplar veneer plywood with edge banding for the most durability.

I've already used a local shop to do the CV on some doors and i'm well aware of their pricing and quality.

Wrong materials choice. Wrong choice period.

Take the 7-9K that spraying a CV finish for a whole kitchen averages, along with the 5K for the Ikea components, plus the 8K-12K or so for ALL of the 3rd party components, (including all of the needed panels, fillers, etc) plus $10 an hour for your labor to assemble it all. Say 40 hours, in order to deal with the 3rd party issues. Spend that 20K+ on buying a good mid grade brand that already has the door color and style and is assembled too. Make your project easier and cheaper both.

Ikea only works economically if you choose all Ikea components for DIY and don't try to reverse engineer factory quality results by parting out it all and choosing amateur quality materials that won't hold up.

Sounds like you got it covered. Maybe I should switch from using the high-density water resistance grade of MDF that I've been using for years to popular plywood that would dent from even looking at it the wrong way.

From the OP:
either way we will be taking them to a local business to have conversion varnished in the color we want

but be afraid, be very afraid!!!

If you decide to go with Barker, order all the materials from them.

I don't understand why you don't have Barker finish the doors et. al for you. Are you using a color they don't offer? I ask this because I'm not familiar with their paint finish options.

@Thor...Be afraid of what?

When it came to our IKEA/Barker kitchen, I have a mix. The exterior of our island and exposed side of the fridge was wrapped with MDF shiplap, which we got from a big box store and painted ourselves. For the toe kick, our plan is to start with IKEA’s Lerhyttan line (and their decorative feet), and build from there. We need to test paint, and see how it looks over the existing finish. The benefit of using a stock IKEA toe kick is that it installs easily with their feet, so if we can make it work, we want to.

As far as side panels and filler... well, I’m torn. I would lean slightly toward Barker, but only if you have a large enough order to qualify for free shipping. Otherwise, I think the price of shipping would skyrocket, because the pieces are so big. The benefit to using them would be that they would match your doors... the paint would adhere the same, the thickness would be comparable, etc.

If you use IKEA panels/fillers, the slight downside would be a question of whether they will take the conversion varnish the same as the bare doors.

I wouldn’t be opposed to building using raw lumber, either. Which isn’t super helpful, I know, but I wouldn’t rule anything out. I think they all have pros/cons.

(And I think it’s ludicrous to expect $8-$12K. I’m about $2k, and I have a very large kitchen.)

Have you asked the company that's doing the finish what they'd advise? If they do this often, they might have recommendations.

(Ignore all the doomsayers here unless they actually explain themselves! :P)

No one is suggesting you spend 100k or anything near that. I 've done highly customized IKEA kitchens in the 12-16 k range. You just have to be aware of the real world cost when you are comparing things. You ask a question here people are going to weigh in with their option. Some of those are based on professional experience some of us build kitchens everyday and some once had a kitchen done by someone in their own house and believed they are now experts. You take your pick.

JDesign, your 12-16K costing was in house cost, using your expensive professional equipment and expensive professional products? 18-30K retail, depending on margins?

I’ve helped friends with IKEA projects, and hacks, and their belief and the real world math never equals out. It’s not a bad product. But it isn’t the best bargain by a long shot once you start down the customization road. Unless you can do all of those customizations in house, with already purchased machinery and a good deal of experience using them. A $900 cheap paint rig blows through a gallon of $170 finish really fast when you can’t get the tip or air setting figured out.

That was actually the price I charged the client. (I know that was too cheap). Kitchens weren't that big and material was Fenix NTM so finishing was involve. The doors were processed on very expensive machinery with zero edge joint technology. These were highly modified and sort of test cases but I someone wanted to put it together themselfs abe just get doors from us (they'll be more than 20 styles) they could easily hit that price point or less.

* meant to say no finishing involve. Material was super matte from Italy.