The AOpen board is a gimmick and nothing else.
Tubes are very sensitive to EMI and there aren't many places in your home with more EMI than inside of a computer. Putting a tube based amp right next to a massive switch-mode power supply is not exactly an ideal situation...
What's more, tubes run hot. That's how they work. The added heat from that device will make quiet cooling significantly more difficult with no real pay back due to all the EMI.
The best option, in my mind, is to offload all your audio digitally to external equipment and deal with it there, be that from an expensive DAC and amp or simply a good receiver.
What pd says regarding the capture cards is largely true. Pretty much all of them suck and can be a pain in the ass. Personally, I'll be using the Hauppauge PVR-250 because it's one of the few cards that's compatible with Win XP MCE and I want the interface to prevent me from having to explain the HTPC to my roommates every day.
If you're married, you'll likely find that interface helpful in dealing with the wife as well...
