How much am I looking at spending on a decent amp for my HD598s?

$200 will definently get you something good enough.  If you want to go portable the E11 will work out great.

For home use try buying a prebuilt starving student.

For sale forums here will almost always net you a good amplifier, otherwise eBay has quite a few.
Just look up the amplifier in the search bar up top to ensure quality.
Little dot MKii or III is a good amp for the price from what I've seen.
If you will be playing music from you computer to your amp you could also get a combined amp/dac which will work out better and bypass the crappy sound card in you computer if you haven't already upgraded it.
Sorry about all the choices, it can get pretty confusing sometimes just don't worry to much as long as it's reccomended on head-fi you can't make a bad choice.
Edited by John In Cali - 10/16/11 at 10:06pm

Imo you don't need an amp for those if you have a receiver or amp out already. I have the 595's and they do just fine from those and even just the out on a DAP. $100 to $200 should get you something just fine in any case, especially used which is the way I'd go.

The HD598s are rather easily driven, so an amp isn't entirely necessary, but $200 has a couple of really good options --

 

Used Schiit Asgard

Matrix M-Stage

FiiO E9 + E7 (or just the E9 if you don't need the DAC and portability of the E7)

If you're using your computer buy a decent soundcard, (asus xonar Dg) or just get the E9. 

Don't get the E9 or anything with a high output impedance. The HD598 is very sensitive to high output impedance.

I find them to be insensitive, personally. They need as much power as my other headphones, and scale nicely when amped. 

Without it, they sound like a cheap headphone IMO. 

If your just doing Stereo 2.0 stuff.

You can get a single tube headphone amplifier on eBay starting at $50, ships from China.

yeah but if we were happy just driving them, then we wouldn't have this forum

 

:)

 

You can always squeeze a bit more out of it with better amplification and/or source.

I've found the HiFiMAN EF2A to be a good match, at least better than straight out of my PC.  Has an integrated DAC and amp, so you can always just upgrade later on.  

They're sensitive to output impedance. I'm not talking about output power, though I'd argue they don't need that. They are more sensitive to output impedances above 6 ohms than other 50 ohm headphones. This is a fact. Look up their impedance curve.

 

I'll even do it for you.

 

As a related aside, they need just under 1V of power to reach 110dB. Pretty much any amp will do this. A Fiio E5 will do this.

Edited by Head Injury - 10/18/11 at 3:23pm

 

Thanks Head Injury. 

Seconding the HiFi-man EF2A. Tubes+ DAC? Yesplzkthx.