lonestar: don't you love how all us demented freaks at Head-Fi are so eager to help you spend your money?
Picking up on Ron's (vedder323) idea of stepping up to 650's, you might consider an extreme makeover. Sell your 600's and amp (should bring $300 - 400 total), add that to your $1000, and now your talking wide open opportunity.
Some pleasing amp combinations that come to mind for the HD650's include:
- Corda Prehead
- Ray Samuels Emmeline HR2
- HeadRoom MAX (used)
- Singlepower SDS (used) or MPX3
- Grace 901 (used)
- and many others that others can/will suggest
You get the idea.
Where are you located? If you can attend a meet, run to one at your first opportunity. If no meets where you live, seek out fellow Head-Fi'ers with gear you want to audition. Most of us love to share this hobby.
If you can't attend a meet, hook up with a reputable vendor with a trial purchase policy - HeadRoom, Ray Samuels, Mikhail (Singlepower), Tood the Vinyl Junkie, and Audio Advisor all come to mind), and try stuff that way.
There is a world of good listening out there, and if you can afford it, go for it.