You need to do a little more archeological digging still. You need to know the whole construction of the floor before you can decide how best to install something new. I'd take up that plywood piece in the kitchen and see what's under it. It's higher than the surrounding floor, so needs to go. You should also be able to see from there what subfloor is under the original kitchen hardwood. It's too bad the space under your entryway is finished, but I'd still do some exploring from below to see what's under there, and to figure out the fix to stop it from squeaking. Is it drywall below or a drop ceiling? I know it probably seems like a pain to tear out drywall, but if you cut out a clean patch, like 2' x the width of the joists, it'll be relatively simple to repair. Just make sure to cut it down the center of the joists so that there's room to screw the patch piece to it later. Cut the hole under the area that squeaks the most, if you can. Have someone walk on and watch the floor from below to see what's moving. It might be as simple as pounding in a couple shims from below, or face-nailing a loose board from above. You want to find out what's underneath the hardwood. It might be laid directly on the floor joists, or there might be 10" wide boards that the hardwood is nailed to. Another thought is to take out a board in the hallway, since that's not original and you want to replace it. See what the subfloor is there. I am a bit puzzled at why, when you've stripped the kitchen down to the original hardwood, it's still higher than the hallway floor. Is your current surface perhaps not the original kitchen hardwood? Peeling back the plywood area will help determine that. BTW, I haven't heard of that stop squeaking product you linked to, so can't offer any personal opinion. And don't pour self-leveling compound over top of hardwood. It needs to go over plywood.

I did not mean to let this thread drop. I want to say again, thank you all so much for your support. Greendesigns, that is probably the nicest offer of help from a perfect stranger I've ever received. And if you ever do roadtrip near Portland, hit Heirloom Roses in St Paul Oregon. :) Update---I did insist they refinish the floors. The GC told me the flooring guy agreed to "take care of the floors" which when pushed I discovered they were going to "repair" (which they'd already claimed to have done) rather than "refinish." I expressed concern over this to GC. They did the repairs last week. The spots are still there. :( Many/most of the spots are greatly lessoned/gone, but the worst spots (the ones in front of the front door and an area in the dining room) are still visible. It was because of those two areas that I insisted upon getting the floors redone. Obviously, I'm not happy and the GC knows this. (I'm sure the floor guy is not happy either because he's now invested another day on this job.) GC told me Thursday that he needed to talk to the floor guy and see what our next step is and I've not heard back yet. I'm sure his next step will be to tell me to shove it. You all understand--this is so exhausting--this has already delayed us moving in for several weeks, we missed our deadline of being in the house before school started because we made the floors a priority. And they're still not fixed! I gave floor guy 2 opportunities to fix it... what would you all do at this point? I am now done-stick a fork in me. I will live with those ridiculous spots--that never should have been there, had he done a careful job in the first place--but I refuse to pay this guy as if he did a good job. He did not do a good job and has shown he is not able to fix it. Does this seem reasonable...I am thinking that I should pay floor guy for materials and installation, but not the line item for finishing? That gives me the option to get them refinished properly later (I know it's a hassle) but then I am not seething that I've paid for/accepted an unacceptable job. What do you think?

I would find a match to the existing hardwood. It looks to be oak (either red or white) in a narrow plank (3" or so). This is super easy to get a match (species, width and cut). I like either natural oak (it will depend on whether or not this is red or white oak) or a light medium brown stain in a transitional/traditional home. The dark cherry window trim indicates that you would want to stay quite warm (allow the red to show through) without turning the floors orange. Once you have the species match, you can have your professional hardwood installer offer several stain samples that you would choose from. In your situation, I would love to see a 'light mahogany' in there. As for the fireplace, it is great! You might want to look at updating the hearth in front...but other than that, just leave it be as it is period appropriate to a 1950's home. And the colour is very, very easy to live with. We've seen worse. Much, much worse.

Floor heights are to be maintained as much as possible (safety reasons as well as annoyance). An option would be to match the SPECIES of the wood you have in the other room, lay it in the correct direction (perpendicular to the joists) and then stain it a DIFFERENT colour. It can be tone on tone. That way you have a species match that, in the future, can have a colour match when you choose to have the floors refinished all at once. Of course you could add a decorative "in-lay" border in the room and then run the planks perpendicular to the joists. The border adds visual interest as well as a raison d'etre for the new floor to run in a different direction. You can make it look like was done on purpose. A solid, site finished hardwood installed by a craftsman installer can get this done in a heartbeat. The beauty of the inlay makes the up-charge worth while.