Need a USB sound card

Hey guys.
I'm unsatisfied with the onboard sound on my Asus p8z77-i Deluxe motherboard.  I need suggestions on a USB sound card.  Because i have no expansion slots in this LAN rig for a pci or pci-e sound card, I've decided to turn to USB unless someone has a better solution in mind.  Case is a Bitfenix Prodigy if that helps with crafty ideas.

  sound card must:

- Have a headphone amp

- Be under $50

- Be small (easy transport in a backpack with peripherals, cables, and powerstrip, etc)

I've heard the Asus Xonar U3 is decent, so i may consider that.

or perhaps ill spend a bit more and get this

Creative has terrible drivers. In original drivers the bass redirection function for 5+1 speakers was not available. Expensive soundcard and I had absolutely no bass. Now i use hacked drivers from net and it finally works ok. But there are no updates available, looks like i will have to buy a new card for windows 8. Won't be Creative for sure.

Well, I am no audiophile so take this with a grain of salt, but I own one of these:

Its very small, under $50, and does act as a headphone amp. This came with my headset, seems to make things sound a bit crisper and cleaner and boost volume by about 30%. Again not an audiophile so I can't really speak to the intricate details of the device. Think I saw a review somewhere of it that stated it was much better than onboard sound, but not as good as a $100+ soundcard.