I would try a slightly different take on Rleff's suggestion and go with a Rowland Model 2. It's a better vintage of Rowland than the Model 5 (many argue that the Rowland 2/6/8/9 are the best Rowland amps ever made). It puts out 150 watts into 4 ohms, but what the amp really brings is refinement and build quality - both superb. Being fully differential balanced like your Atma-Sphere amp, it should substitute well for it with regard to cabling. It does not run particularly hot. Try to find one with the battery power supply - when run from batteries, there are only a small handful of solid-state amps that compete with it. PS - Like Rleff, I ran the monoblock version of this amp (Model 6's) and it was amazing how similar it sounded to my no-feedback triode tube amp.