[shawntp]

I just got a pair of HD600's for the first time.  I used to own many Grado's (usually ran un-amped) and departed headphones for a while for speakers.  I recently acquired the Senn's in getting back into headphones after a hiatus (forgot what I was missing).  I think the HD600's were the headphone for me all along, I just never gave them a try.
 
I currently only have a M-Audio ProFire 610 interface.  The HD600's sounded good but weak out of my iphone/macbook but they came alive and were pretty full and amazing out of the 610 with the volume near max.  I am wondering if a moderately priced dedicated amp around $200 used would be a worthwhile upgrade or if the 610 is going to be on par with anything in that range.
 
I was specifically interested in the RSA Hornet as a portable, but really just want to be able to take the headphones around the house and to different spaces.  So 610 vs RSA Hornet vs other ~$200 option vs just wait and save  
 
These are the 610 specs:

Headphone Outputs at Maximum Volume into 32 ohm Load​
Frequency Response​	+/- 0.1dB, 20Hz to 22kHz​
Signal-to-Noise Ratio​	-108dB (A-weighted)​
Dynamic Range​	108dB (A-weighted)​
THD+Noise​	0.003% (-90.0dB), 1kHz, -1dBFS​
Max Output Level into 32 ohms​	+2.9dBV, typical​
Power into Ohms​	60 mW into 32 ohms​
Output Impedance​	75 ohm​
Load Impedance​	24 to 600 ohms​
Crosstalk​	<-75dB @ 1kHz​

 

[Ham Sandwich]

If the FW610 is anything like my FW410 the headphone outs are very underpowered.  Adequate maybe for IEMs.  Can't drive Grados well.  Drives the HD600 like mush.  I consider the headphone outs on my FW410 to be useless.

 

[shawntp]

Not sure if this is the relevant measurement, but in M-Audio forum I read the following differences in specs:
 
ProFire 410 Max Output Level into 32 ohms - 3.5 dBV, Signal-to-Noise Ratio -101 dB  
 
ProFire 610 Max Output Level into 32 ohms +2.9 dBV, Signal-to-Noise Ratio -108 dB
 
I guess if nothing else, it appears they are not exactly the same.  I can say there is a big improvement in the 610 compared to the headphone out on my MacBook (sound gets bigger, tighter, and with a little sizzle).  I suppose this is just wetting my whistle, I have no concept of what the 600's can do.  I might pick up a used amp and see if I think its worth it or not.  I record with the 610 so its always useful as a DAC.

 

[Ham Sandwich]

I've got the older FW410.  It's about 8+ years old now, I think.  The headphone out specs are going to be different from the new versions.  If you've got a mixer or monitor control you can try those headphone outs as well.  They may be more powerful than what is on the 610.  But more powerful doesn't always mean better and they may or may not suit the HD600.
 
The Schiit Asgard is a nice amp for the HD600.  It's $250 new, less for B-stock.  It's a desktop amp.  Worth a look.  It's on my short list for a second amp to pair with my HD600.