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How come you left crab air out of interest?
Are you planning on replacing the rears only or looking at fronts as well?
Why not look at a set of Brembo's for the front? Set off a DC5 will fit with S2000 disks (so I'm told). Might save you some pennies.
I'm not sure it's worth the hassle to be honest, going rate for DC5 Calipers seem's to be around £450 then they need reconditioning, Maybe £50-£100 for new seals and painting. S2000 StopTech disc's £155, Pads £55, Add all that together and it's getting close to the price of the stoptech touring kit.