headphone amp

That is pretty sad to hear about Singlepower. I had one of their amps about 10 years ago and thought it was pretty good... Sorry to hear so many people got screwed! Hopefully you paid with a Credit Card and could stop payment.

Headamp always seemed to be more geared toward the Grado band and Headroom always seemed to favor Sennheizer (very general and IMO). I have owned a few Headroom amps and a few Headamp amps and they all were pretty good. I felt that Headamps were better buys but I have not heard Headroom's newest line.

I would argue that you look for an amp to drive the Sennheizers well. Most anything that can drive the Sennheizers will drive the Grados with ease. Keep in mind the Grados are 30 ohms while 650s are 300 ohms. But some amps may be better suited for Grado because of impedance matching.

I heard the woo amps at RMAF and they were very impressive.

If you want to go with Headamp, then go for the GS-1. It's head and shoulders above the Gilmore Lite (I have both) with better transparency and space. It works well with both Grado (I have RS1 etc.) and Sennheiser (I have HD600).