The PCM2706 is about the cheapest USB DAC solution out there, I guess. It sounds quite ok though, but nothing special. I prefer the output of my Sony Minidisc Deck (MDS-JB920 w/ 20bit conversion, SP/DIF connection from iMac) connected to the line-in of the v8.
I don't hear much of a difference between the v3 and v8, but I didn't get the chance to compare them side by side. The v3 was already out of stock when the v8 became available in Europe.