I'm going through the same thing, been sitting on an Aero AR10 lower for a year, decided to get components now due to the laws in WA state going whacko and availability of Aero being a potential issue...that's because I wanted an Aero upper to go with it as well, and mate up solid. I too have a bolt 6.5 but want to do other calibers and was looking at 22-250 but read similar stuff. I don't have a .308 but settled on that for now due to it being a solid go too, ammo is easy to come by for it and cheap, and I have a 6.5 for longer range. I do want a .243 as well since I don't have that, but was leaning 6 creed or 6.5 grendel?? that would be for an AR15 lower though, from Aero as well, so just ordered a plain upper for that as well, that I'll build at a later date and decide what to do. I got my uppers for a pretty good price on a good sale at Primary Arms, way cheaper than aero site, could just get the upper for now and components later when you settle on what you want, that's what I'm doing anyways, so they mate up good, will go with other companies components for the other stuff. Glad this thread popped up, just what I needed to read!