Accustic Arts - Wadia?

Has anyone compared DAC I-MK4 or TUBE-DAC II to other DACs in this category, and specifically to Wadia 521 or Wadia player 581iSE with digital inputs?

Also, has anyone tried to connect Accustic Arts directly to amp? Am I right in assumption that TUBE-DAC II would not perform well in such scenario due to its analog stage?
I should clarify, I would connect DAC via a passive resistor based volume control, reason being that I do not find active pre-amps transparent, having Wadia connected directly convinced me this is the way to go.
So I am interested to hear opinions on AA DACs in comparison to other DACs and specifically Wadia, connected in whatever way, as well as any experience with AA connected directly via some transparent passive volume control, reason being that not all DACs have analog section good enough to accommodate such connection.
I have the Accustic Arts Tube Hybrid in my system, you can read a review of it here on the GON, and recently was at a friend's house who has the Wadia dual DAC/controller head reference unit and thought his Wadia digital front was the best that Wadia has produced and was a real pleasure to listen to, however I did not believe it out performed the AA Tube Hybrid DAC sonicly. Also remember that that the Wadia cost almost $30000.00 more then the AA piece.

I have listened to the top of the line Wadia pieces in the past and never really liked them, not very musical/organic though very detailed/powerful sounding, this new Wadia is very musical and for my ear's very different then the "house" sound that Wadia used to have.
I have seen your review, which was one of reasons for this question, to see if others have arrived to similar conclusions.
Do you recall how your friend’s Wadia sounded new, was there a significant improvement over time, and if so, how long it took Wadia to sing?
The Wadia is detailed, presents a layered and proportionate soundstage, can detangle a congested passage, is taut in the bottom end, and conveys subtle alterations in rhythm.

Not all music benefits from these attributes. The Wadia will allow you to listen to the performers and the recording, deficiencies and all.

It really depends upon the music you like, how you listen, and what you appreciate in audio reproduction.
I recently replaced Metronome C1A tube DAC and T1A drive with the AA Tubedac 2 and AA Drive1mk2. The latter is definitively the more musical. Sound is fluid and detailed, very natural sounding. Altough Metronome is ofcourse not bad at all, it lacks the same degree of realism and relaxed sound AA offers (and it is way overpriced). Before Metronome I had the Audio Aero Prima DAC (also with tubes),but this converter never reached the same kind of fluidness and sounded rather 'harsh' and 'cold'. As far as I can judge within my system, you can't go wrong with the AA TubeDac2.