Well just my 2 cents but.....
I owned the 2Stepdance, I researched it a lot and had several conversations with Jan himself regarding the SQ of the 2Stepdance compared to the original (OPA121 compared to OPA1611) and he assured me that no comprimises were made with the SQ of the 2Stepdance. I say this because I never compared the original Stepdance with the P4. I did however compare the 2Stepdance with the P4 and sold it fairly soon after as the P4 was superior in many ways and as a bonus cost less also. The P4 is an amazing amp. I have (and have had) quite a few portable and home/desktops and I can tell you the P4 punches way, way above it's modest price tag. With the right chipset (yes this can add to the overall cost) it can compete with amps costing considerably more,
I am running OPA627AM's in LR + HA5002 Buffers and ISL55002 in G/VG at the moment and I am astonished by the SQ and versatility to cope with IEM's and full sized cans. The other thing to consider is the fact that you can tune it to suit your tastes and phones by swapping out the opamps and/or buffers. I doubt I will ever part with my P4.