I will admit I did not sand my old cabinets at all - but they went into the laundry room which is not a high use area. That was about 20 years ago and they are fine. I used Zinsser 123 primer which actually says you do not have to sand. I did clean very well and the cabinets were not high gloss. I did all my trim the same way. Zinsser BIN is supposed to be even better at sticking without sanding. It does take time for both of those primers to cure. You can topcoat, but the primer can take up to a week to cure, so don't go knocking the doors around till the cure time is up.

I just did the EXACT same project in my guest bath. Painted the vanity white, the walls seafoam green, ripped out an ugly cabinet & purchased the frame for the mirror (haven't put it up yet). This is the only pic I have handy to share, it was time consuming, but easy... i should've done it years ago. My advice is buy the BEST brushes/roller/tape your hardware store sells. Good luck!

And here's a long shot of the total effect. They look a lot like built-ins. Because they AREN'T built-ins, we left a bigger space above the counter (partly because the TV needed it, but even if it hadn't, I'd have left a space so it looked like there was a "reason" we switched from one to the other. NOW...our fireplace is a bigger focal point than your TV, and our wall juts out there. So we left that big display space. Plus, we have no windows. In YOUR case, w/ those windows taking up so much of the wall, and your TV so low (and it being a TV, which to me is more functional and less decorative), I might consider whether I wanted a built-in look in the middle as well--sort of a "full wall" effect, wall-to-wall, floor-to-ceiling, with an empty space where the TV goes. If I wanted to do that, I'd want a backing on my upper shelves so it looked more like the whole thing was one unit. And with a "full wall" effect, I might even consider whether I wanted it all to be painted the same color as the other walls (or maybe white like the woodwork), so it was less like "kitchen cabinetry" or "furniture" and more like "part of the room / woodwork." That would keep the full wall of storage from overpowering the room, perhaps.

The original factory finish does not need to be sanded off. 🙄 Scuff sanding is sufficient if it’s bonded well. A smooth, tight-grained wood like maple is a good choice for a paint substrate. But, the paint grade that lasts the longest is going to be MDF, and you can’t get that stained. Aftermarket painting is not cheap. 7-9K, to add to your budget. A solid wood door will have normal expansion and contraction that will show a lot more with a paint coating. Be sure you understand what that means. And be sure that you understand the processes that a true cabinet refinishers will use. The products will not be homeowner grade paint. Join the Kitchen Cabinet Painting Experts group on Facebook to learn the right way.