Thanks for all the suggestions, gents.
After a bit of online research I'm going to try an Azur 851N, looks like just what I'm after. If it sounds good through the on-board dual-mono Analog Devices DACs (as all reports say it does) then I can sell on my current DAC (Bryston BDA-1) which will pretty much cover the cost. Found a brand new one on ebay for my 1K budget.