Do you know what caused the buckling (water damage,nails pulling out)? If it was water damage you really have to check your subfloor. Also your subfloor should be a min of 3/4 in thick (being an older house it prob is, just have to be sure its still good).
As far as using unfinished flooring, the material is a little cheaper but there is a lot more work involved. You have to lay the floor then sand it smooth, clean it very well and multiple coats of stain/poly. The sander rental and added materials (not to mention labor cost) will bring the cost back up to if not more than prefinished anyhow.
I know you want to keep the same look/color as the rest of the place. You have to figure out what kind of wood your floor is. I also recommend pulling up a board (out of the floor your going to replace) that the color still matches the rest of the house and start hitting the stores to find your match. Even if you go with unfinished your going to have to find the matching stain/poly.
In all honesty I would really recommend going with a 3/4 prefinished hardwood. Its the same as what you want "regular hardwood" just minus the extra work and time. There are so many options as far as color and grain you will find something to match.
I used to rehab houses. If you have any questions let me know.