Are you looking specifically for a Sunn power amp? If not, pretty much any pro caliber amp is stable at 2 ohms.
Crown Macro Techs are old school lead sleds but are pretty reasonable because of the big weight.
A great option would be if you can find a Stewart World 2.1; 900 watts X 2 @ 2 ohms, dual monaural, the only thing the two sides share is the power cord and a central fan, separate power supplies and power switches.
Best of all the are US built professional caliber SMPS amps, only weigh 17 lbs., and can be had for around $500 IF you run across one. They show up on eBay sporadically.