You might want to keep in mind that the HD600s are one of the most comfortable pairs of headphones (better than the AKGs in my opinion).

Per my original post...as a general rule, if you could only make one choice, what do you think matches well together best:

$700 amp and $1,300 source or
$1,000 amp and $1,000 source or
$1,300 amp and $700 source?

I'm just trying to get a feel for this. For example, when I first started investigating this, it didn't seem to make sense that people matched $300 cans with a $1,500 amp. I thought, why not $900 cans and $900 amp. Now, I understand the difference and why. Likewise, I'm trying to understand the best match between amp and source, pricewise.

There are plenty of options, the price ratio thing never works... It's all about how things work out together, no one really ever knows, because a good system is all in the hearing of the listener. Personally, I always choose the headphone or speaker to get first, then work out the rest of the system based around what ever source I choose. Even though I say put the highest priority on the source, it's still heavily dependant on a good balance whether or not your system ends up sounding good to great.

Presuming you could pick the best equipment at each pricepoint, I'd say$700 amp, $1300 source.

For your type of music...I would recommend a stax classic system or lambda nova system.