Similiar questions like your are often answered on this forum & the usual answer most ppl agree on is 2 12" . 10s are a bit small on SPL but great on SQ , 15s are leaning to more SPL than SQ , while 12s are right in the middle with nice tight loud bass - SQL .
2 T1 = 1200wrms 2 P3 = 1000wrms really hard to definitely say unless some1 here has actually done it .
Seem like u are looking at the 1000/1200 rms range of power to your subs . If u like the rms on the T1 series ,Y not buy 2 12" T1 then - i would . Is $ the deciding factor ?