Call up DC. If there is not a dealer close enough, they can work with you directly. They have outstanding customer service. And a product to match. The IDQ's are great woofers, but don't love crazy amounts of power. The other option would be an IDMax. Incredible sub. However, more money. Another sub i feel i need to mention is the JBL Gti mkII.
I do not have much personal experience with Memphis. So I wont try to compare anything directly. If it helps, my DC Level 4 12 ported @ 32hz hovers over most others around for SQL. And i'm proud to say, Including JL W7's. Just remember the biggest part of how you're setup will sound is your box. Also, Fi Q is a nice SQ(L) woofer. Moderately priced. You could also look at the SSA Dcon, Icon, Xcon depending on budget and power. Hope this helps your search.
Edit: I may as well add, if you have heard the Memphis and you love them, don't second guess your ears. However, all the woofers mentioned above are very, very good at doing their job.