Keep in mind - I'm running the 4 BK Advances, not BK LFE's, which are significantly smaller (11 lbs vs 5.5 lbs). The BK Advance has a power handline spec of 75 - 400 watts vs the BK LFE of 400 - 1500 watts.
I have no doubt that you could run 4 BK LFE's, if you are not maxing it out. Buttkicker's website actually highlights the wiring schematic for 4 BK LFE's off of 1 amp. But I thought I better mention the power handling specs vs amp output specs. I have no experience of running 4 BK LFE's - I did run 1 BK LFE off the same amp, which shook an entire couch with ease. Sold the couch and bought 4 recliners from rtheaters - the LFE didn't fit. I tried 4 mini's, but was not happy with the result. The Advances were an excellent compromise.