How can my system top out for max performance?

ok, i have a JL Audio 13.5"w2 and a 900 watt planet audio mono block amp. I made my box and system from the ground up. I have no additional room for more speakers and the box i made has the max amount of air space needed to get the most potential out of it, without being too much, and its vented. So the box is perfect and cut for a 13.5" cirference, so 13.5" is the only way to go. Honestly i cant complain at all on the way it sounds now, because it blows most everyone else's system out of the water (around here anyway lol). But i am definately a b guy and im always looking to top it out. So my question is... what is the best possible setup to have using my box with a 13.5" sub. i have wondered if changing amps would help, or going for the JL w6 or w7 would help. Or it might even be that i could change both and sell my current system and go with the new 1000 watt JL amp with the w6 or w7.... But these are just some ideas i have had, so im really looking for some good advice on this. please comment! thanks