It should get pretty **** loud and have plenty of thermal handling past the 800w or so you are gonna give it. Your new box gonna determine wether or not it is gonna be a louder setup. I would do a 1515 they are only 450 rms and 1800 peak so 7-800 is gonna get it really loud without really hittign any thermal handeling limits. Call DD and see if they take 8-900rms on the 1500 series, I bet they say to go for it.
How about a Fi SSD almost a perfect match for your amp.. Just go big ported and tuned fairly low.
The DD i would port according to recomended MFG spcs.