Two strokes will cost less than a hi-performance 4 stroke... cams, seats, valves, etc just costalotta! But some swear by em and I am not knocking 4 strokes at all. The KDX is as close to a 4 stroke as any 2 stroke I know of and reliable as anything on two wheels. You will be impressed with the sheer grunt power right off idle...if the jetting is close. There is a lot of help available in that regard.
I always like to have the seller tell me how he maintained it...in his own words...without me asking. Just a test of credibility. Thats not to say the one you buy (used) won't need a topend overhaul ($115 to $180 USD is typical) If you buy new its easier. It is also widely reported that the KDX220 will require a Wiseco in order to avoid a known piston issue that may or may not occur, but the cost of a failure is very high and the change to the Wiesco relatively cheap(115USD+/-) The KDX200 seems to have escaped the problem. I have a 220, but the guys on 200s SWEAR they're better. Both bikes require new fork springs almost immediately unless you weigh under 90#. But they are cheap and easy to change(got to do mine yet) the stock forks are goofy soft but Honda xr400 of some series or other slip right in
By the way, my XL600 Honda single doesn't have near as much snap off the bottom end of the rpm range as the KDX220 does.
Lastly, the 220 will haul your 220# at least as well as my 220#+ It is more than adequate..and I like power!
You'll have fun on whatever you get!!
Greg