I'd recommend (by personal experience) a Go-Vibe V5, especially for Grados. I bought one mainly to use at work with my Ety ER4S - with which it has a nearly "magical" synergy. After I heard the V5 at home for awhile with my Grados (SR60 and SR225) and the Koss KSC75, I bought another V5 as a home amp to dedicate to my Grados. As a point of comparison, my other home amps (compared to which I prefer the V5 for Grados) are: a PPA v1.0A retro-fitted with discrete buffers (which I've tried with AD8610's, AD8065's, and OPA627's), and a high-bias M^3 with STEPS (which I've tried with AD843's and OPA627's). The Go-Vibe V5 just produces a lively, "live" and realistic sound with my Grados like none of my other amps, to my ear.