As for OP, I would say keep the W7, sell the W3s... and when you get an SUV or whatever you were saying, get another.
W7s arent the end to all subs, like wenn_du_weinst makes it sound... They are great subs tho, and sound very clean. Get a nice 1k amp and go about your business, then when you get another car get another W7 and another 1k amp or a 2k and sell the 1k. Should be a very nice system.
Idk how much you can sell it where you live, if a lot, then cool. Subs you may want to look for are things on the line of Sundown Z, Fi Q, Arc Flatline, things on the line of that. They will all sound clean, but get louder than the W7...