Greetings. The 650 is not an unreasonable bike to start off with, but I will tell you that the 250 is a lot more bike than people realize. The lack of fuel injection in mine is probably a bigger issue than the displacement. : -P
If you're into tinkering, a couple easy mods I did were to replace the clutch plate springs with stiffer ones from Barnett and replaced the shifter spring with a stiffer one. I like knowing that I've actually shifted rather than assuming that I've shifted just because I've hit the limit of the lever. Price on it was obscene though.
The other nice one, is to replace the stock levers with ones adjustable shorty ones. Just do yourself a favor and pay the money for good ones. Or just adjustable ones, it's nice to be able to adjust them so that they activate where your hands are strongest.