The Pentax K100d I brought nearly 10 years ago for £160 works still works OK with SLR lenses in either PK mount or M42 mount, as well as with various enlarging lenses etc for macro work. All the lenses I had before getting it where manual focus models, but I added film era AF lenses after getting it & had no issues using them either. It's not a model I'd recommend anymore things have moved on so much, that cameras with better low light performance, higher resolution & better battery life can be brought for very little extra,
However as I like playing with adapting lenses I've switched to mirrorless systems for my everyday cameras. These allow a wider range of lenses to be adapted, give the ability to enlarge the image in the viewfinder for critical focusing, and in the newer models also have focus peaking for a quick guide on focus. I've not yet tried Konica AR or Exacta mounts on my mirrorless cameras but I think I've now tried all the other reasonably common SLR mounts as well as several rangefinder mounts.
I've not had much experience with Sony Alpha DSLRs (only handled two) but I don't see any particular reason to go for them (unless your lenses are Minolta A mount). Sony's e-mount cameras (mirrorless rather than DSLRs) are flexible and a good option IMO. The Nex 6 I brought over a year ago would be at the bottom end of your price bracket & is a reasonably good camera. I found the spec.s on earlier NEX models had significant factors that put me off. If you feel 'full frame' is a real benefit the original A7 might be just within your budget - depending on quite what you mean by a couple of hundred (I think they're about £400 now but haven't checked for quite a while).
If you really want to have a DSLR & mirrorless doesn't suit you then the main factor is what mount your exisiting lenses are.