The Bryston Cubed series- specifically the 7B and 28B double from 8 to 2 ohms although their advertised rating stops @ 900 into 4 ohms. A talk with the principal James Tanner will confirm this. (owners of specialty HiFi products are surprisingly accessible)
You can get a pair of 7B SST mono blocks for 4-5K these days. That's a LOT of amp for not much money.

