The only way you can run XT's is as separate units, if that is what you are asking. There is no Master/Slave, you need an LT for a slave.
But otherwise connect up both units but at first connect USB to only 1, update the firmware, then USB connect the other one, update it's firmware.
Sometimes Aquasuite gets confused when you are configuring controllers if there are multiple Aquaero's in use, but nothing you can't work through. I run 2xPro's in my rig.
8x pumps sounds pretty ambitious, post up some pics or links when you get it all going.