What have you looked at so far? Do you want to stay in the large trap format? What exactly are your needs for "keeping up" - are you intending to have one box per side? Multiples? If multiples, how do you manage comb filtering vs. coverage? Why do you want powered?
The only spec sheet I can find on the SR4732 is this one:
http://www.jblproservice.com/pdf/SR-Series/SR4732.pdfwhich is incomplete at best. Max SPL seems to be about 130dB, but no coverage info is provided, and no response graphs are provided either.
The obvious popular powered boxes that are quasi-similar are the QSC KW153 and the Mackie HD1531. Other choices include the RCF 4Pro 6000-1 and a few others in the same general shape as what you had.
Since you don't specifiy a budget, I'm assuming you have infinite money. The JBL VP series is extremely good:
http://www.jblpro.com/catalog/general/ProductFamily.aspx?FId=16&MID=4and many of the other big names (Meyer, EAW, etc.) have powered offerings.
You have few options for powered dual 18" subs. You have a lot of options in powered single 18" subs from all of the above mentioned vendors, plus some interesting horn loaded ones from Danley that can be ordered in a powered configuration.
As to powered vs. unpowered - I used to want only powered gear - plug it in and go and all of the box tunings and limiting are handled by the manufacturer. I realized that requirement ended up limiting my options quite a bit and bit the bullet and bought a passive system with a proprietary controller that ends up doing the things I wanted, and for the size of the system, an extra small rack with amps and processor didn't really make much size difference.