I think whoever said that the headphone out is running through solid state is incorrect. If you look at the wiring picture from the bottom there is a brown wire that connects to the board that goes to the output stages from the tubes. Furthermore, when you press the TR/UL button it makes the same sound changes that it makes with the speakers. Additionally, when I have put some noisier tubes in, it is definitely audible through the headphones.
I think the sound difference people are experiencing between the headphone jack and the speaker taps has more to do with output impedance and power. I compared this amp with my Woo WA-22, both with good tubes on the Woo (CV181 T2, NOS WE 421A, and WE274b replica on WA-22) and on the R8 (Sophia Blue KT88, Sophia Blue 6SN7, NOS Tung Sol 6SL7, and CV181T2). I also tried the R8 with CV181 Treasure 2, KT88 Treasure 2, as well as with PSVane EL34 PH Grant Fidelity select. The R8 is every bit as good sounding as the Woo WA-22 IMHO on my Abyss Diana Phi. Obviously there are slight differences in the sound depending on the tubes selected, but they are both fantastic and any differences could be adjusted using different tubes. In some ways, the R8 is better due to the higher output power, even through the headphone jack as compared to the HE adapter. So don't feel like you have to use the speaker taps. I don't think you can do any better for $1500. All that being said, I have not heard this with the stock tubes as I bought it used with the above really great tubes, so YMMV.
As for speakers, the R8 handily beat my Luxman L550AX on my Harbeth P3ESRs.
