My preferences so far with the LCD2s in terms of digital source is as follows:
1. Audio GD Reference 7
2. Muse Mini DAC TDA1543 X 4
3. Bryston BDA-1
4: Silicon Chip DAC kit
5. Dacmagic
6. Pioneer Elite DV79a
7. Ipod Classic 120GB (6th gen)
From 1-3, these dacs do not induce any significant fatigue. From 4 onwards, these dacs, I find fatiguing, which manifests itself in a lethargic sensation and an inability to focus on the music within 20 minutes. 1,2,4 and 6 produce a tonality I prefer - where tones are a little more fleshed out. 3, 5 and 7 sound leaner. However I believe reducing digital fatigue is the primary concern when selecting a DAC. Tonal preferences are subjective, although I find Burr Brown chips favourable but I ultimately prefer the R2R architecture over any of the DS architectures I've heard. Hopefully soon I will be able to listen to a dual mono balanced Buffalo 2 using dual Sabre DACs in it's ultimate configuration and provide some feedback. This beastie has 4 toroidals feeding separate analogue and digital sections, it is being built by Wink.