On their web site it shows that 7ft3 is optimal sealed size.
As for the EP2500, it seems to be close in specs to the Crown K2, which I used to drive a pair of 15" sealed subs. I've since changed to a pair of BASH 540w plate amps, from Parts Express. As good as the K2 amp was, the BASH amps provide more output, plus having the option of either using the builtin crossover or the LFE input, which you don't get with a stereo amp.