270 is a great round, and actually as big as I would ideally go for antelope, I started off with a 270 and now have a .243win pretty much exclusively for antelope hunting/dedicate rifle, also my new varmint /coyote rifle though too.

Lot's of great options... 25.-06, .257wby, 270win probably gives you more versatility though, maybe consider the 270wsm too?