I've had the 901 for four months now and it's the only amp I have that can play a Grado to an AKG1000 perfectly, plus since it's DAC is better than the DAC/Analog stage of my DV47A that is also a big plus. I still have not heard any solid state amp in it's class to compare it to. The 901 exhibits control over the Grado HP-2's, 325's, & RS1's much better than the EMP or RA-1 for that matter. Every instrument in it's space, completely non grainy, very musical, endless bass that doesn't muddy up any of the other frequencies.
When I get the Impedancer for the RKV, in less than 2 months hopefully, this will be the 2nd amp that will work with all my phones.
So far I prefer the K1000's with the RKV, and the EMP pairs wonderfully with the W100 & W2002, but the 901 OWNS the Grado's and dependent on what material is being played it sometimes owns everything else also.
I love the tube amps but if I was forced to have only one amp it would be the 901.
Now go ahead and buy it already, you know you want to.
I have a recent review in pdf format, if anyone is interested e-mail me and I'll send it back as an attachment.