First, how do you like the way the system sounds. Are you happy? If you want more bass maybe reconfigure your box, a slot ported box tuned (most cookie cutter round port Curcuit City boxes are crap tuned to 45hz Yuck) in the low 30's would give you 2-4db gain without $1000 missing from your wallet.
Second is the A5 and Class D amp? if it is, they are not digital and wont be as clean as a regular class AB amp causing "coloration" or bascally more distortion.
It is hard to underpower a speaker to the point where it becomes bad for the woofer. I think you'll be fine with the amp you have, but you may want to look into a different box.
