Of course the easiest way to do what you want to do is to install a different width in the kitchen and use something to act as a transition between the two floors. If the kitchen section will be at the same finished height and you can and want to weave new into the old, then you will have to have oak milled to your 2 1/2" size. Not impossible, but will cost more than factory runs at the usual widths. I don't have pics for you, so I hope someone does and can post them for you.

Redroze, I'm just getting back online and seeing your questions, so I'll try to answer what I can. My new floor in the LR/DR was not pre-finished, it was all site-finished. I did put a pre-finished floor down in my office (no pics, sorry) because I work from home and didn't have time to be without my office for the week it would have taken to have floor sanded etc. The pre-finished does have a different feel to it than the site-finished. I wouldn't say it's grooved, just a more defined difference in between the individual planks. The office doesn't adjoin any other room, except the tiled hallway, so I didn't worry so much about the wood being different there. I see from your pictures what you mean about running the planks the same way and wanting to be sure things don't look odd. One idea might be to take up some of your FR planks, like the first 12 or so, and then put them back down interwoven with the new planks. That way there's not a clear line in between the 2 rooms, but rather a more gradual blending. Here's another couple of pictures, this time of my family room. The first one is a before shot of the hardwood floor + a rug-like carpet. The floor created a frame around the carpet. I had the carpet taken up and new hardwood put in where the carpet originally was, then everything sanded and refinished. You absolutely can't tell where the old wood was vs where the new started. In this case, the new is random width because it opens directly to the kitchen (as opposed to the LR/DR which is all the same width). So, one house, all new site-finished floors in the LR & DR, all new pre-finished floor in the office, original/refinished in the kitchen, and half&half refinished + original in the family room. Boy did we have dust! Hope this helps! New:

My concern is the layers of vinyl underneath the hardwood. Hardwood doesn't like sitting on vinyl and vinyl doesn't like sitting on hardwood. The two do NOT like each other. If you think this is a good idea (which it is considered on the technical side of things a horrible approach to this) then you might have to add another layer of subfloor. A nice, fat, thick 1/2" plywood to cover those two layers of vinyl. Now you can go ahead and lay the hardwood. Technically, my suggestion is hideous. It is atrocious. It is so "unprofessional" that I could weep. But if you insist on leaving the vinyl in place, then you need to think of a way to separate the vinyl from the hardwood sitting on top....and one very sure way is with plywood. Again, my suggestion is a travesty. Then again so is laying hardwood over two layers of vinyl. In the flooring world, we 'allow' ONE layer of resistant flooring (like vinyl) to sit underneath another floor. For example: the first layer of vinyl was considered "OK" to lay another layer of vinyl over top. All good. No one in the technical department batted an eye. If a THIRD vinyl floor was proposed (or a laminate, or linoleum, or cork, or hardwood, or tile, or even carpet) it would be a "NOOOOOOOO! STOOOOOP! DON'T DO IT!" type of answer. So I will officially say: No. Stop. Don't do it. There. It has been said. That being said, if you as the homeowner choose to forgo the installation instructions and the "Best Practices" as set out by the National Wood Flooring Association (as homeowners your word is "law" when it comes to things like this), you are welcome to go ahead and lay hardwood over two layers of vinyl. If you do it, I suggest a new layer of plywood to help things along - because you need FLAT. And most "old hardwoods with two layers of vinyl sitting on them" are anything but flat. Good luck. You would be better off remediating the asbestos/vinyl and getting down to bare hardwood. Now a new floor (with the help of a layer of plywood) can go down. Or you remove the original hardwood with the vinyl (this is easier to do than scrape off the vinyl...and easier = cheaper) and start with a new layer of subfloor and go after it like it should be done. But as homeowner your word is "law". If you tell a professional to "just do it", they will say "yes ma'am/sir" and do it. But they will not warranty their work. You will be left holding the bag - and all the pit vipers that lay inside. It's your call.

Go for it. I would throw down some 3mm or 6mm cork underlay down (it floats just like the hardwood) and then float the hardwood. Use a high-quality joint glue on the hardwood and you should be fine. Besides...if it gives up the ghost in 10 years, would you be upset?