[twizzleraddict]

I'm going to throw the Burson HA-160DS, despite the fact that it's above your budget. If you save enough, it'll give you a DAC and an amp that pairs very well with the HD650. I'm using it in my rig and the more I listen to it, the more I'm forgetting about the gear and just listening and grooving to the tunes. It's really giving me a final nail in the coffin on requiring anything additional (READ: Upgraditis!). 
 
The HA-160 is just the headphone amplifier product from Burson but it should have similar characteristics, although not sure what DAC you'll be using it with.

 

[nymarty]

Here are my rcommendations from my own research.

Tubes:
Bottlehead Crack (DIY for $279) -- perfect for HD650 and what I use for mine
Little Dot 3 or 4
Schiit Valhalla (more of a hybrid but well reviewed and well matched to 650s)

Solid state:
Schiit Asgard -- for $249 and 15 day audition window, you can't go wrong

Good luck.

 

[IEMCrazy]

I would hope in two years the OP would have settled on an amp by now!

 

[twizzleraddict]

 
Quote:

I would hope in two years the OP would have settled on an amp by now!

 
Yup. I think this thread is still alive because folks, like me, who were researching options for our newly acquired HD650s would find the recommendations still relevant and also current. New amps come into the market and definitely change the recommendations somewhat over time. 

 

[IEMCrazy]

 
Quote:

 
 
Yup. I think this thread is still alive because folks, like me, who were researching options for our newly acquired HD650s would find the recommendations still relevant and also current. New amps come into the market and definitely change the recommendations somewhat over time. 

 
The funny part is there are so many similar threads, I've no idea how this old one managed to be salvaged!
 
But while it's alive, I'll be one of many to throw a recommendation for Schiit Lyr, just below the stated price point if a DAC isn't needed, and really opens up the HD650s a lot in terms of soundstage, presentation and avoiding the "veil."  It's my preferred amp compared to Headroom Micro (Desktop) (old mid-2000's model), my Onkyo & Denon AVRs.

 

[saggett]

I've tried the iBasso PB1, Fiio E9, Audio-GD 10SE and RSA Hornet with the HD650. Ranking in order of preference:

1. RSA Hornet. Wonderful clarity, can pick out instruments with ease, voices have no grain and sound natural. Bass impact is a little lacking compared to the 10SE but not weak or ill defined,
2. Audio-GD 10SE balanced. Wider soundstage than Hornet, but voices less natural, details less clear. Can't hear subtle details like breaths and room echoes as well. Bass is forceful and clearly audible even at lowest frequencies.
3. Fiio E9. Narrow sound stage compared to others, but a decent performance with grain on voices nearly absent. Bass is reproduced to lowest frequencies.
4. iBasso PB1 balanced. Good sound stage, but more grain than Fiio, Audio-GD or Hornet. Reasonably neutral, and bass frequencies are reproduced with impact, but muffled and grainy.
5. iBasso PB1 single ended. Definitely not recommended for HD650. Lacking definition, grainy, bass is not reproduced fully in lowest frequencies.

My next step is to build a Objective2 amp, as given the above I'm fairly sure my listening enjoyment is primarily determined by THD rather than power output. I'm hoping the Objective2 amp with THD measurements as low as the Hornet but with more power (essentially, two 9V batteries instead of one) will tick all the boxes.

 

[mac336]

I used the nuforce icon HDP with my 650s when I had them and I honestly didnt find them any better than the NFB-12.  I would recommend bottlehead crack, little dot, or schiit valhalla.