Expensive option: R1150R/RS/RT wheels fit straight in and have the speedo drive. K wheels don't have the speedo drive as it is driven from the g'box on these. The rear on these is 17"
Cheaper option: R1100R/RS/RT wheels also fit straight in as above but have an 18" rear wheel and take slightly narrower tyres (160 rather than 170/180)
The other difference is that you can swap your current brake discs onto the 1150 rims but must get different discs for the 1100 ones. If you want to be able to swap back & forth, you will want two set of discs anyway so it doesn't matter so much.
Personally, I went for the 1100 wheels as they were v cheap at £75 for the front & £25 for the rear. I sprayed them matt black and had BT020's fitted. Including the discs, I spent about £350 all in. The 18" rear wheel has a slightly larger circumference than the newer 17" ones, roughly the same as the standard wheels (with the higher profile tyres) so they don't gear the bike down like the newer ones do. This keeps the acceleration/top speeds similar to standard.
HTH, but post any questions & I'll try & answer them. Coolcarbon has done a similar swap with the K wheels - looks really smart.