BaDDaK

I need some help with a few questions,
i own a regular cab pickup and currently have 2 10" RF HX2's in an approx 1.4 ft3 sealed box powered by an 800a2. i am currently looking at purchasing a set of IDQ12's and was planning on cutting the current 10" holes larger to accomadate the 12's as space is an issue and a larger box is not an option. how well will these subs perform in 0.7 ft3 each? ID recommends sealed boxes between .55 and 1.0 ft3 but will i sacrifice the SPL i have now or will i still retain that and gain a little SQ as well with the small box space. am i better off sticking with my 10's or trying the 12's?

thanks in adavance