Man do these threads get old.
If everyone that claimed to shoot 600-1,000 yards with HALF the accuracy that is reported in these types of threads, there would be records falling left and right because the posters would be pushing the real evil genius, scientist types of the shooting ( the real benchrest guys ) to even higher heights.
To the OP - You are on a very good route. The .270 is a good cartridge and will do the job. The problem with the WSM and the WSSM rounds is that they do cause barrel wear much faster than normal, so factor that into the equation, especially if you are going to be buying a custom barrel at some point.
Unless you are just dying to get that money out of your pocket and towards a new stick of some sort, might I suggest a little reading.
by Maj John Plaster (Ret.) is a great read and will teach you a ton about long distance shooting.
Extreme Rifle Accuracy by Mike Ratilin(Raitlin - something like that).
And a subscription to Premier Shooting Magazine.
Good luck and keep us posted on your results.