What PSW to buy

So far i have been looking at two different powered subwoofers...

+Polk DSW Pro 600 12"
+Dayton T1503A 15"

My system has no subwoofer out nor multiple rca-outs, and i figure i would need some kind of Y-rca cable to get the signal from my preamp to the sub and to my power amp.

I am going to be living in college dormitories for a while, so obviously it could be argued that either of these are a little bit overkill. Mainly i want very deep bass and low frequency reproduction that will sound tight and good at lower levels (and of course good at high levels as well....)

Any thoughts / recommendations?