I disagree with sov. I think you will be completely satisfied with your hd580's. I own a pair of hd600's, which are very similiar, and i think they are spectacular for nearly every kind of music. I am using an Antique Sound Labs MG/OTL Head with upgraded tubes.
You can go here to see a bunch of pictures i have taken of it:
http://www.imagestation.com/album/?id=4290766347
You could snag one used if you wanted to keep your budget low. There is a new one coming out with some minor upgrades, it will run approx. $320 - $340 .. You could get one now from holm audio for $300 (older version..the one i have, no complaints here). Or find one used for about $250 ..
To get the sound you seek I think you will not want to settle for much less.
The only thing is, we have only covered a few of the compenents needed in an optimal headphone setup. Im not sure if you have a good cd player ..Im guessing not...or good interconnects (rca cables, you can get some outlaws,they are supposed to be good budget IC's. for 50 bucks).
If you want to get some truly high end sound you need to cover all aspects of your system.
1. Cd player - I reccomend the c521i from yawa.. refurbd for $219..
2. Interconnects - Outlaws seem to be the ultimate budget interconnect.. you can find them for under $50 i think..
3. Amp - I, of course, reccomend the asl mg/otl head. ($250 at lowest)
4. Headphones - You already have a great pair in the hd580's.
5. Headphone cables (optional) - To get an even better sound you could get a pair of replacement cables for your hd580s from equinox or cardas. Equinox cables run appx $200.. cardas $150. Total optional but a very worthy upgrade if possible ever.
So, in my opinion, the minimal amount you will eventually have to spend to effeciently accomidate your hd580's to get the sound you will want will be around $500.
Keep in mind you can get it in steps.. Get the amp first and use a dvd player until you can afford the cd player.. Then get the cd player.. then get some interconnects.. etc etc.. By that time you will be planning for your next headphone setup
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