I've had plenty of subs in the past and by far the best is the current JL 10w6v2, its running 500w rms from the JL 500/1 and sounds great ported or sealed. I use to run 2 pioneer 12's of a PG amp in the past and this 10" keeps up with them.
With it sealed its got a tighter sound with a slight loss in sound volume, its opened my eyes to having decent bass and not just loud thuddy bass. Wasnt cheap though, the sub was £300 and amp £400.