Weighing in on HD650's vs. SS vs. tube amps:
HD650's are warm yes, so are tube amps...BUT the thing is a high impedence can like the HD650 or Beyer DT880 (600 ohm) requires lots of voltage, whereas lower impedences require much more current. Much of that HD650 veil/dark signature comes from them not getting the voltage they crave. Tube amps are much more capable of delivering the voltage necessary to drive the HD650 to its potential. I loved my HD650/Little Dot MKV (solid state) combo, and thought it couldn't get any better. THEN I got the Woo 3+ (tube) and realized what I'd been missing. The great thing about the HD650 is how well they scale with other equipment...sure, they sound great with a great sounding solid state amp, but they will absolutely destroy your expectations on a good tube amp. All the talk of them sounding dark or veiled or rolled off in the treble vanishes with proper amplification.
Yes, you want to strive for synergy, but don't get too caught up in the "tube amps are warm, SS isn't" thing...it's fairly subjective, and isn't really 100% accurate...if anything, that tubey warmth is more accurately described as "lush", "rich", or "sweet", compared to solid state's "fast", "crisp", "bright" or "detailed". Your source (medium, DAC, etc.) is going to have a great impact on that as well, so you need to look at your system as a whole, and what you want in the end...but no amount of trying to match "silver cables, because they are brighter than copper" to offset "a dark sounding headphone" can make up for poorly matched electrical demands.
Hope that helps...now, back on topic...sorry to threadjack.
