There may be some folks around here with some first-hand experience with the KEF 3005 , but in the meanwhile I can at least offer some thoughts on crossover points...

I'd definitely not use a crossover lower than 80Hz. You might even toy around a bit with a 100Hz crossover for the satellites (fronts/surrounds), although the center is probably going to be good at 80Hz. The subwoofer should have an option for disabling any internal crossovers, which is going to be preferred (let the receiver/processor handle the bass management). Unfortunately I couldn't find a manual to verify that.