Which subs to consider given my conditions?

Ok, so this is another "which sub" thread, but mine is a little specific. The sub needs to be a 12 and I currently have a custom built sealed box thats is approx 1.5 cubes of internal volume. It will be powered off a Hifonics 2006D which is somewhere between 1500wats rms-2000watts rms at 1 ohm (never bench tested it). I want a sub single 12 that is a good mixture between SQ and SPL. I am getting rid of my new style RE XXX as it as musical as I would like ( the lows are great but not the higher frequencies). So given this information give me some suggestions to look into. Thanks in advance.