A great DAC to get started with would be a Firestone Audio Fubar II or a Firestone Audio Spitfire. I own the Spitfire which has coax and optical inputs. However, in your case you want a USB so the Fubar would be perfect. I have owned the first edition of the Fubar and it's a great, fun little machine. USB input, RCA ouput.

Here's a great review on both from 6moons:

http://www.6moons.com/audioreviews/a...2/candy_3.html

They sell on Ebay but have a look here as well:

http://www.audiophileproducts.com/

The best feature with any version of the Fubar, and there are now 3, is they are plug and play. No software at all!!

There are tons of USB DACs out there harley. Also check out these guys. HotAudio are Canadian, handmade USB DACs. There are about 5 or 6 different models, each with different features. These guys sell on Ebay mostly, check em out too if Firestone is not to your liking or outside of your budget. These are fun little machines too, entry level but don't doubt their ability.

HotAudio on Ebay:

http://stores.shop.ebay.ca/Personal-Audio__W0QQ_armrsZ1

Happy Hunting Harley!! Hope this helps...