I think I'm going to do the 4 12's. The install will be a little easier. The power requirements will be a little lower (to start) and I have more options with subs. I think for this winter I may start with FI Q's or PAP WMD's then upgrade to FI BTL's or DD 9512's at a later date. When I can afford the power.
I was just thinking I may start with the BTL's and underpower them for a while. But this way I won't be wasting money on subs that I only plan on using for 6 - 12 months like I did with my 10's I have now.
If I'm really poor this winter I may just do 6 10's using three of the tens I have now and buying three more matching ones, but they are only 500 wrms tens. They are good but nowhere near where I want to be.