Would you prefer 5 1/4" or 18"?
I think a few more specs might elicit a more reasonable answer. Without giving away too many secrets, how about whether you're looking for a sub suitable for ported, IB, or sealed enclosures?
This
http://www.partsexpress.com/pe/showd...number=295-455 will handle 350 watts at 8 Ohms.
Paul