I would expect your equipment to provide great sound in a home environment. I'm not familiar with the KEF speakers, but I see that the amp can provide four 90 watt outputs for the speakers. The cables between the Saffire LE and the amp would be unbalanced phone plugs to RCA "phono" plugs on the opposite end. I'd start with a main HW channel using the Whafedales and the sub in combination. Check the sub's manual for possible ways of connecting but I'd tend to start with the main channels going to the sub and then on to the Wharfedales if the sub supports that sort of connection. If you have surround sample sets or reverb software then perhaps the KEFs are the rear channels. Later you can experiment with a separate pedal channel for the sub if you like.
There are so many possibilities, but the main point is that this equipment can produce excellent results. Down the road a larger sub might add something. I've run speakers from both PA amps and from a Sony home entertainment receiver and can't say I hear a difference at normal listenning levels, except that the PA amp's fan is a huge distraction at the moment so it will either get mounted inside my console or I will go back to using the Sony.