5 to 10 HZ??? Why such low frequencies? AFAIK I don’t think there’s anything out there in the standard audio market that can reproduce these frequencies, and if there is you will need good monitors that can reproduce them, and then again if you find monitors that can reproduce them, do you have the ears to hear that? (or most likely feel it?).
Ah ok, a scientific purpose a la “Mythbusters”, well I’m really not sure about common USB devices with such low frequencies, I use M-Audio Fast Track Pro and the range in it is 20Hz-20KHz
what signals do you intend to send to the woofers? if it is just simple sine or square waves you might be better off by using an arduino. you can either program it to send some low frequencies or you could control it via puredata…
the rme multiface goes down to 5 hz even in 44.1 khz maybe that is out of your budget or you don’t have the expresscard slot. generally you are in a really bad situation with a usb2.0 audio device on linux. you are much better off by using a firewire device or rme expresscard.
sorry to insist once more. i would strongly suggest not to buy a usb 2.0 device to use with linux. maybe you can tell us what your problem with firewire is and somebody can solve it.