In the spirit of this site, I bought a spare AR lower from Palmetto. With that out of the way, I need an upper. Already have 2 complete 5.56 rifles and a 6.8. So, for the next one do I go big with a 458 SOCOM, or small with a .234 Valkyrie, or some other caliber? Normally, I buy the ammo and then find a firearm to use it in, but with the available choices, it is all very confusing! So what would you do?