Yeah, there are some USB 2.0 interfaces that can do it, though anything Line 6 is not among those ranks IME (as Petrovsk himself admitted, though it's not really an issue). But that's only for one or two tracks simultaneously; the bottlenecks would definitely creep up with a few more I'd imagine. And if you can afford a firewire interface, why would you even consider USB 2.0?
Oh no, I'm not considering USB 2.0 interface, I was just thinking if it is possible to go that low with USB, it just has to be alright with FireWire I'm pretty drawn to the Profire 2626 for some reason... it feels like I haven't even given the Focusrite Saffire Pro 40 a chance yet, I haven't read much about it... almost spent all my researching on the Profire instead :| I'm gonna head down to the local music store tomorrow to try and score a good deal on either one of those interfaces but probably the Profire, and if I can't, I will just have to order it from Thomann