Have you concidered a 200 KDX? (or a 220) Great bike to get back on the saddle, very reliable, loves the woods and you can get them for really cheap. You can probably find a good one with all the goodies (FMF pipe, DF3 reeds...) for 2K$
I've had mine for 2 years, love it and only tore down the engine last week for the hell of it, everything check out, no rebuild necessary.
Beside, doing a top end job on a 2 smoke is simple and way cheaper than a top end on a 4 stroke...
As far as power, I have no problem with hill climbs or staying ahead of any 450 (CRF), 250 CRF and other 450 KTM I ride with...unless it's wide open where I have to cheat a bit to stay in front :boss:
Remember that riding fast is 10% bike and 90% rider not the other way around
My 2 cents
Wilf
PS the KLX is weak compared to a well moded KDX and the KX is a monster, you'll need to modify the KX quite a bit to "tame" it for the woods and you'll still have to ride it quite aggressively...