223 for sure.
If you do a little shopping you can find a Savage 11FXP4 with a scope for around 500. Better trigger and stock than the Stevens.
Howas are good also could go with a .223 and their .204's are tackdrivers and death on wheels for yotes
A Marlin in 243 would fall in your price range, another good choice
Ruger in 204 or 223
good quality 223 ammo is just as expensive as the 204 or 243 so I would not let the cheap ammo pitch effect my purchase if I were you.