Is there a headphone amp in this price range to drive the SR-009 great?
Please give me some recommendations. I might just afford the SR-009, but definitely can´t afford a 5000$ amp.
You could theoretically get a used KGSS for not much more, but I'm not so sure it'd drive the SR-009 "great". Your price range is really scraping the bottom of the barrel though, the only options in your price range that I'd personally consider are the Stax SRM-323S/II and SRM-717.
If you can't afford a better amp to go along with the SR-009, I'd recommend not bothering at all. You'd be better off with a Stax Lambda-style headphone like the SR-507.
If your source isn't appropriately "high-end" either, the SR-009 would just reveal its shortcomings as well.