The HA2 has a dac, but its far from as good as the DB2 or the DacMagic - Its decent though, but just for a kickoff its 16/96 single chip where the two others are 24/192 dual chip, so not much competition there, the two amp compartments are completely different though, as one is balanced solidstate and the other is a hybrid and not balanced. Both the DacMacig and the DB2 has balanced+singleended outs by the way.
As for what my ears tell me? They tell me that with the current buffer/amp setup in the PB2, it and the Argon sound very similar, bot have lage soundstages and refined sound. The Argon is simply a bit more warm/round...Its hardly noticeable, but in side by side testing and quivk switching between the two it sometimes noticeable. To describe the differences:
Highs:
HA-2 is warmer, slightly fuller sounding than the PB2, which is a bit sharper - its an imensely small difference, but its there...
Mids:
More or less identical
Bass:
The HA2 has a more pronounced and full bass, where the PB2 is again sharper and more precise
I think these probably sum up the normal differences between solidstate and tube amping, from what I've read. I amp hopeless at deciding because the difference is so small its rarely, even on this sidebyside test that i notice it, its so little that sometimes i wonde if its actually there or my brain is messing with me (It has messed with stuff pretty severely before)
Edit: Form-factor is sort of worth noticing too...The "desktop" rig is..Well..About 20 times larger than the other i thing - which is also why it baffles me that the difference in sound is so small...