Hi Macrojack - I got the Altmann BYOB amp and have been using for a week now (not as much as I'd like as I'm recovering from an operation). Anyway, I connected the amp direct to my Tom Evans Groove Plus and fired her up. Initially I found the sound to be quite similar to my Avantgarde Model 5 amp but somehow more relaxing to listen too. The bass is really solid and tuneful, mid range is very natural and top end slightly less emphasised.
So in summary I think the Altmann is terrific value and drives the Duo's to ear-splitting sound levels if you wish. But the funny thing is that I can't really be worried to listen to all the hi-fi criteria, I'm just enjoying the music.
Anyway, you said I'm adventurous and I am - I've ordered the Attraction DAC with all options. Charles Altmann emailed me today to say he'd shipped it so I'll post a further update once it arrives.
(T/T is Avid Acutus/SME V / Dynavector 17D3)