sorry about this... it slipped by me, i havent been checking the forums as much lately. you could fit an 8" in there, i've seen it done, personally i think it detracts from the interior though. but that is just my personal opinion.
if you are overwhelmed with the info you should consider copying my setup. i've spent the hours and the money on trying other setups and i'm very happy with what i ended up with. check out the link on my sig and i think i have a break down of everything that i used on page 3 (may be page 4,5,or 6 but i think it's 3

)
feel free to bug me as much as you want...it's a cool toy to have in your vette