Take a look at the F407, it's a couple years old now but in terms of ability and sound it's still a fairly impressive amplifier. Also it has a very comprehensive crossover network, which would allow you tune a 2 way system without an external crossover. I have a 4XS but haven't set it up yet. In the meantime the amp's crossover is doing very well.
You can set the levels at anywhere from 40Hz to 8000Hz. That way you would avoid sending the Vifas anything over 4000, which is where you should really be cutting them out anyways (I would recommend the cutoff point be lower than that too, but it's more than adequate as a temporary setting)
