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.