NewYorker,

There is no professional sound card that is USB2. The professional audio and video community has adopted firewire. USB is useful for other things such as midi interfaces. The theoritical speed transfer is as not important as the practical rates of transfer with reliability and support. Will this change in the future? Maybe. But if it is changed, I would suspect Firewire2 will be introduced over anything else.

The best card will be simply determined by your choice of Software. Are you going Steinberg Cubase or Nuendo path? But you really cannot buy any professional USB2 audio card. It simply does not exist.

The examples mentioned are not professional and will even cost you more money. Because you will find out after buying them, that they will not do the job and so you have to buy another one from scratch. But that really depends on you. What are you trying to accomplish. Are you trying to build something professional?