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.

If you pulled out a piece of baseboard somewhere, you would see what the last 3/4" of flooring looked like. If there was vinyl underneath, you could carefully cut with a knife until you reached the wood. Bear in mind there may be 1/4" plywood under the vinyl, too, to be cut back. In all likelihood it will be a softwood floor (pine or fir). Not to imply that pine is bad, quite to the contrary; that's what I have and it's original and lovely. Casey

Im confused..... You say you want "real hardwoods" on the stairs and prefinished "real hardwoods" in the bedrooms. It sounds like you're wanting the same "type" wood with the same "type" finish and the same "type" top coat on it. You know that apples-to-apples thing. So why not prefinished for the stairs too? Then it is the same. I doubt you would save any money by having an installer finish the wood for you. But, if for some reason you need one stained and one not then have your installer bring you samples of the stairs that he has match-finished. Or, if you plan to do this yourself- have an actual paint store (not HD or Lowes-- but a paint expert) "match" the prefinished "real hardwoods" for you to sample stain several pieces on. See if it looks "real" enough to you. We did that when having our alder cabinets stained to match the knot colors in our unstained oak floors. BTW....Engineered is real wood with several layers under it that criss-cross (usually 5-7). In some areas of the country people are advised not to put down solid hardwood that might "pop" on cement floors. This is usually the case for those that live in the western states as almost all homes are built on slab. Laminate is basically a photograph. And just like any photograph some are bad and some are great.

Thought I would also update this thread since it popped back up. We moved into our new build 2 months ago and ended up choosing engineered wood for most of the house, except the mudroom, laundry room and their connecting long back hallway, which got tile. I can close this area off and the dogs stay here if we are gone for several hours. Their food and water is also kept in the laundry room. The floors are Duchateau - Riverstone collection - Sava color. So far they have not shown any scratches from the dogs making the crazy run to the front door when they hear the doorbell and/or fedex! The floors have a rustic look and slight texture that will make it easier to hide any scratches and dents.