where to go from here

hey there all,
I am currently rocking the 1997 Avalon XLS, ovbiously from the login name, I have a clarion drx9575xz as my head unit it's going to a directed 600d mono amp pushing my dual Kicker CompVR's the dvc ones, and to a Phoenix gold 200x2 amp that's pushing my MB Quart reference series coax/components. The interior speakers are running as two channels, L and R. The main reason that I joined this forum, aside from talking with other toyo lovers, is to ask for suggestions/ advice about how to deal with my subs. I love the CVR's and I am a big fan of fifteens in general, they are however in a slightly undersized sealed box and I think I am losing more of the lower end than I like. I was wondering if anyone out there has built any box/ boxes for two fifteens I have them running in series, bridged to a 1ohms load. My major concern is not about interior trunk size, but about getting this in the trunk, the biggest box I've gotten in there is 17x14.5, height and depth (the length isn't really an issue, my current bow is 36 inches, but at least 42 could fit. Give me any suggestions you have. thanks