I had an 83 CR480 and for an old diasour (but new back then) it would rip. I mastered the 3rd gear launch quite easily. Most guys we rode with had 125s and 250s, so it was good for showing off. No matter how long the straightaways were, it could carry the front wheel at will-any speed, any gear. It made for a fun bike. The only bad thing is the brutalness of the thing- instant wheelie, instant roost, instant gas cap in your face-. I learned really fast to keep my toes on the rear brake. Funnest bike I ever had.
My heavily modded CR 250 was just as fun. Keep it pinned and jam through the gears without any fear. It too would wheelie in every gear but with less rush factor. Always predictable, more nimble and much faster lap times.
If you can handle the 500, go for it. It is a beast and will put the moxt experienced on their ass. The 250 is strong, more predictable, and still powerful. Have to decide which would be best for you and your terrain.
---TEX---