I have experience with the saffire (full version) Mackie, and RME firewire interfaces and would say that the RME is the most reliable and the saffire the least reliable with the mackie being quite good, it just lacked a couple features that I needed. All of them sounded pretty good, but ultimately I am using the fireface 800 and not the other two. I'll cut you a great deal on a very slightly used Saffire if you want it though
BTW, all my experience is with PC/Sonar.