Oh, on getting a really expensive interface, and this as someone that has one that costs about a grand: it doesnt take all that much money for the interface to be far, far, FAR better than the monitors, the room and the mics.
Its a question of what youre willing to go for to kill the bottleneck. I got a fireface in part because I never wanted to worry about my interface, the dacs and the pres, again. I wanted to know that they werent limiting me, that I was limiting me or the room or the mic location really does suck and so on and so forth. So I can trust it basically.
You dont need to spend that much to get something that still exceeds everything else you'll be using (most of all the room and cab location).