Agreed I wish they had a compatibility list. Not 100% sure if the T12 will fit my Node 304 or not. If the reviews turn out to be good though, I think i might replace my Tower cooler to free up some room.
You got those at a steal of a price. I've been wanting to hear the Dali Mentor series for a while, everyone who owns them seem to rave about them. I'd love to hear your impressions once you receive them.
I'll jump into the fray.
Personally I think you should forgo getting an external DAC with your receiver initially. Your AVR has preouts and be used as a preamp, I'd just get an amplifier to go with the Maggies. If you still feel like you're missing something then I'd consider getting an external DAC.
I don't think you could go wrong with Yulong or Audio GD. Unfortunately I haven't heard either so I can't really share my thoughts. Personally if it was me though and I had to decide, I'd go with Audio GD.