To power the subwoofers I used the Hypex NC500MP module. It is a nice, compact and efficient 500 watt into 4 ohm class D module, more than enough power to feed the Scan Speak 30W/4558T00 woofer. I like having a bit of headroom available in an amplifier.
This is the same power/amplifier module as is used in the Hypex FusionAmp FA501, a plate amp to power active subwoofers with an onboard DSP module.
As I have my own chain of DSP, I did not want that extra AD/DA step of the FusionAmp. I was able to get my hands on a pair of the NC500MP modules, not easy as they are sold as OEM only. For those without a DSP chain something like the FusionAmp FA501 can certainly be a viable option. Be sure to add your own enclosure to seal off this plate amp on the inside of the subwoofer.