I have the 2170 in as a loan again (my friend's away on vacation for a week) and the DA100->252S->207 combo sound absolutely fantastic... Enjoying it as much as my LCD-2's right now.
I said this before on the main Stax thread but the only two weaknesses I notice with these balance wise is that the frequency extremes are slightly rolled off on both ends (I don't quite get others calling these bright, but then again bright to me is a Grado/Beyer type 10k peak... these don't have that, at least with my DA100 DAC), and bit of a midrange honk pushing some vocals to being shouty for certain songs with upclose vocals (but makes the vocals nicely intimate on songs that have vocals backed off a bit). Other than that I find these headphones very even sounding overall, with the typical Stax ethereal presentation, nice open soundstage and good amount of detail. Comfort will be bit of a hit and miss with Lambda frames due to their long cups clamping down at the bottom of your chin, but for 1-2 hour listening sessions I don't find it to be that big of an issue, and I happen to be very picky with comfort...
Again, I do encourage others curious about Stax to give these a try while they are relatively cheap to get. Almost considering it myself right now to get as an alternative rig though I'm not sure how much use they'll get once 009's are in...