Ideally I think what WmAx suggested is the optimal setup if I had the money (and patience) unfortunately I do not.
I have tossed and turned about getting two PC12-Plus or one PC13-Ultra but I think to do the two subs correctly I would need to invest in an external crossover which I do not have the budget for considering that the two subs is close to my budget.
I called up SVS and talked with them for quite a bit (on 2 separate occasions, I'm sure they are tired of me) and based on my volume (4500cf) they feel the one ultra would be plenty and with that I ordered the PC13-Ultra and now can't wait for it to get here. Longest wait ever.
I am definitely interested in the DIY subs though, I think I might tinker with a small one for my bedroom or office and work my way up.
Thanks for all the info, can't wait to unpack the ultra (might have to take a day off work).