In my setup, similar to what you are trying to achieve, I went with the Tascam Dm24 and have never regreted it. It now has the 24 i/o firewire card available. I have had my Dm24 about 2 1/2 years now. It was fabulous at the price I paid for it then and it is a incredible deal now that it has been superseded by the DM32. If you have not already bought something else, it may be worhwhile to check one out. Btw, those strange direct outs on the Onyx could be tdif or maybe you just need a breakout cable.

Regards,

Danny