I had a First Watt F7 and a Pass Labs XA 25 and ran Heresy, Forte IV, Zu omen DW, Zu Soul 6, and other speakers. It was awesome. I did not lack for power on the F7 or XA25 but the XA25 was faster, more quiet and a ton more power.
Not sure if you have pass labs and are looking for speakers or the reverse but I highly recommend the XA25