Best sub to take 600wRMS in a 1.0cu/ft sealed box?

I had an Ascendant Audio Arsenal 10" planned for this install when I purchased it over a year ago (procrastination is a *****!), but I now have a new cat (2010 WRX) and I can't find this **** sub. It's possible that it got lost in the process of moving, and I need to face the possibility that I'll have to take the hit and buy a new sub (doh).

I have a 1.0cu/ft sealed box and a JBL 600.1. Just looking for recommendations of what's good out there for these specs. I'd love to keep it under 250$