I'll agree with the HO when you're looking to get a good sub on a budget. It's very much in line with a W6 in terms of output and SQ. Other notables I'll mention are:
Incriminator Audio Flatlyne (should be about $350 each) - Underhung 3" coil and about 600W RMS rating. Would take the power from your amp well and leave plenty of headroom to cover rise and give your amp some breathing room. SOUND INCREDIBLE
DC Audio Level 3 - Very musical subs with a focus on low-end extension and output. Standard 3" coil and 900W RMS rating. Can definitely take more, should you decide to upgrade your sub stage. Subs are built by hand in Vegas. I saw a pair of used 10" Level 3 up in the classifieds somewhere (either here or on MAF) for 200 shipped each
SSA GCON - Another assembled-in-'Murica sub, it's a good all-arounder but needs a ported enclosure for sure. Another 3" coil, this time with a 750WRMS rating. Go for about $250 each on SSA's website. @denim should be able to tell you more about them if you're curious.
Any one of these subs should do well on the power you have to give and the space you're looking to keep. I would personally go with the Flatlyne, mainly because I'm already considering a build with a pair of these on 1.5k in a Tahoe.
