I disagree. Grados are singularly well-damped. (See some of purrin's graphs and reports on Grado decay.) Connecting them to the current-FOTM super-low-output-impedance amplifers causes them to over-damp, resulting in the harshness and tizziness that many people cite for their dislike of Grados. The reason Grados do well with many tube amps is not necessarily the "warmth of tubes," but that the output impedance is quite a bit higher than your run-of-the-mill low-output-impedance SS amp. Grados do quite well on 15 ohm output impedance and higher.
This gets complicated to a certain extent because the low impedance of Grados causes fall-off with OTL amps as lowering the bass cut-off point results in extremely large and super-expensive output capacitors (which means shortcuts/cheaper alternatives are often used). Hybrids experience this fault, too, because many of their output buffers still require blocking caps and unless sized large enough, cause bass roll-off or phase distortion in low frequency response.
Bottom line, for the best sound with Grados - finding the right amplification is not necessarily so simple.
I couldn't agree more.
A lot of amplifiers do work well with Grados due to their (Grados') low impedance & high sensitivity. Heck, they sound pretty good straight out of the iPod.
But to get your Grados to sound their best you'll need to search for the amp...OR select from my list
Beginning with the least preferred :
3. EAR HP4
1. MAD+ EAR
Just get the Mapletree and you'll save a lot of time and money.