2 layla 3gs. Older xp drivers were great for me, and the new win 7 drivers are fucking solid. 1.6ms input latency for tracking is the best i've ever had, rme, presonus, maudio, and digi included.
That being said I've always held the opinion that fire wire was a stupid idea for connecting this shit. PCI has never given me a hiccup.
Echo's conversion has always been really good! Wouldn't for anything but an alpha link.
