There's 4 main options for pre-built multi channel DC controllers
1) LOR QMB-16D-QC 16 channels. Pro's. LOR and dmx native support, 2 voltage channels (eg can switch 24V and 12V), onboard fusing Con's. can be hard to source late in the year
2) Ray Wu 27 channel (Rita HT712) 27 channels. Pro's. cheap, dip switch selectable start channel, inbuilt led test mode. Con's. no fusing, low'ish current, leds remain on if dmx signal is lost, cannon type dmx connectors, only 1 voltage source
3) DC48. 48 channels. Pro's. Aussie built, great support, possibility of overnight delivery in Aussie, leds fade to zero if dmx signal is lost, high current
4) DC 24. 24 channels. Same pro's and con's as DC48 but half the channels and only 1 voltage source.
For a list of available controllers see
http://auschristmaslighting.com/wiki/index.php/ControllersAs far as AC dmx boards I think that at the moment all there is is either LOR or DIY ones. I believe that there are 1 or 2 under development though.
If you have access to a variable supply try starting low and then winding up to 32V. I do believe that people are using them at around 32V though.
With the leaping arches the heads get joined and the tails go back to the controllers to be switched.