Looking for a USB Headphone amplifier

I am currently using a Music Fidelity OBH21 amp with a V-DAC to drive AKG 701 headphones. Though this system provides detail, I would like to improve on the ’soundstage’ and add a little more bass.

To this end, I am looking for USB headphone amplifier and also may upgrade from the 701s. Would like to purchase the amp 1st, one that would support a headphone upgrade.

Any recommendations?

Your lucky day. Go to monoprice, search tube amplifier and there you will find, for $150, a small tube amplifier with a headphone jack. I've purchased one. Find out what value is all about. Be sure to share, and write the first review. Yes, the good things in life can sometimes be very inexpensive.
The new Ayre Codex would be my first choice. If that's too much, the Oppo looks like a very good choice.
Buconero, I checked out the amp on monoprice. For that price it might be fun to own one. What is the tube compliment? Was not listed in monoprice. Have you driven speakers with this amp, or just headphones? As for the functions I am looking for in a headphone amp, I am not sure it will fit.

ZD,I am sure the AYre is a fine product however I am looking into the Oppo as my budget is, $500-$700, new or used. Also the Audeze Deckard. Possibly the MarantzHD-DAC1. A friend of mine owns a SChiit Vahalla which I will try out. Am sure there are others to be considered.

I am taking my time with this quest as I haven’t thoroughly deciphered how I want to approach this. Considerations run from a stand alone amp with separate DAC to an all in one DAC, amp, pre. Also, I realize that it is the amp/headphone combination that makes for the best sound. I own a MF V-DAC II and can’t help think it is as good of DAC as any to be found in a Headphone amp in my budget. I also own a MF V-link which would serve an older DAC lacking async USB. However, an all in one product might serve me well in my secondary system, which gets moved around.

Back to my considerations, I am looking forward to other’s suggestions.

OK, after much consideration I have decided to look for a used stand alone headphone amp and use a separate DAC. My thinking is that I will get more AMP for my $$$ and greater flexibility with this approach. My budget tops out ~ $600 for the amp (again used).

Any suggestions for an headphone amp that one feels is better than the Creek OBH-21 (original version) within my budget?
Have you looked at the PS Audio Sprout? It was just reduced to $500, which is within your posted price-point. It's an "all in one" that has both a headphone-out as well as speaker posts. I haven't tested one myself, but it has been receiving good reviews.

Hope that helps.
If you live in the US, give The Cable Company a call. They have a lot of headphone amps/dacs in your price range. If you take advantage of their demo program, they'll send you a box full of demo units so you can try them all at once. They also sell your Creek, and will be able to make some comparisons for you.
Courant, thanks for your reply. I am familiar with, and had considered, the sprout. However want a stand alone amp.

ZD, great idea, thanks! I should have thought of CC myself. I will give them a call.
Any thought on the quality of the Benchmark DAC-1 as a headphone amp? As compared to my OBH-21?
I bought Oppo HA-2 headphone amp recently and it sounds amazing. It has asynch USB, SPIDIF, DSD an analog in/out.  I use USB.  Sounds better than my Benchmark DAC1.  D/A converter IC is SABRE 32-bit. It has lithium battery and can be used with a phone, but I’m using it as stationary unit only (next to my computer).

Thanks kijanki, I took a look at the Oppo.  I have not made any move as of yet.  I am keeping an eye on the used market.  

I purchased a used Schiit Vahalla tube headphone amp here on AG. I will use it with a Music Fidelity V-DAC II and MHDT Paradisea+ DACs. Currently to drive my AKG 701Q headphones.  One day I what to try a Audezen headphone however not sure the Vahalla does well with phones having ~30ohm impedance, as do the Audeze models.