So 300-400 for the sub alone, or for both sub and amp?$300-400 and no amp maybe a 15 would be a good choice
15" subs;
Alpine type R
Kicker CVR, CVX
RE audio SE,SX
MTX 8500
FI audio( dunno any model numbers)
Fusion (one mentioned above)
Eclipse Titanium (or any TC Sounds subs)
Just some I could think of off the top of my heAd.