coopersport, XX will only fit your Five with the 26-39 rings, not the 28-42. The chain would hit the main pivot bolts as you shift, trust me, i have played with a lot of these bikes, and played with a lot of dual ring set-ups.
Nick, the £106 price for the spider and rings is/was a mistake. I spoke to them this week about it. The rings and spider supplied on the EPIC are different to the STD XX rings too, as well as the rings and spider fitted to Cannondale cranks, they are different as well!
The correct price is £23.99 for the inner ring and £103.99 for the outer (still much cheaper than XTR, although Madison have just dropped prices to combat OEM sellers/price shaggers)