[Eldin]

I suggest getting a Prometheus 6.03mm tightbore, a tightbore will improve your accuracy significantly and range a bit, you could get a longer barrel and extend it into a silencer.
For a new hopup, just get a bucking, not the whole hopup.

If you want more range, get a new spring and piston. You'll want to get a new piston because the compression on most stock AEG's are horrible.