Motu 828 USB or the Focusrite saffire 40?

[Sound]

http://www.focusrite.com/products/saffire/saffire_pro_40/

www.motu.com/products/motuaudio/828mkII



Motu 828 mkII USB or Focusrite Saffire 40 + PCI card to firewire?

My computer is based in one Athlon 2000XP running at 1.6Ghz, and the mother board is one ASUS A7V8X wich not has Firewire but have USB 2.0, that I don’t know if they are the “high speed” ones required for the Motu, Are they?

Basically I would like to be able to use all the inputs for recording although that usual will be only one, and use all the outputs in order to send them to an analogue mixer.

I have read that Motu is better machine but also I have read that the communication through USB consumes more CPU than the firewire. Will be enough my CPU?
And if I choose the Focusrite 40, I will need a PCI card to firewire. Could it be a problem?

Any experience with those sound cards will be welcome as well any advice.
Also if any of you have tested directly the performance of the Motu 828 firewire versus the 828 USB I would like to hear your opinion.

Regards.