A couple of years ago I was feeling a little randy and bought myself an over the top (price, that is) USB - Shunyata Sigma.
Lucky for me, it was like verdant's acquaintance spoke about, it transformed my system performance. I'm not happy about spending that much and am sure a higher value could be found. I just haven't been motivated enough to experiment since possession is 9/10ths of the law. ha
Still have some guilt for outlaying that kind of cash...
Forgot to mention I had a Totaldac usb and a Curious USB cable prior.