I posted this in a different forum, but got very little input, so I'm trying here  Hey
Thanks for all those that chimed, or are chiming in. I'm a total n00b when it comes to AR stuff, so all help is appreciated.

Want cost effective?  Just replace your A2 upper with a flattop using your existing barrel.  Then sell the A2 upper on the EE and recoup most (if not all) the costs.

Lots of options when building a 'tack driver'.  Personally I'd get an Oly SUM or DPMS upper before going to J&T.

Oh yes you can use the charging handle and bolt carrier for a new upper.  Generally you don't want to be swapping bolts back and forth as it increases wear and you could get into an excessive headspace issue after a while.  Best bet is to buy a new bolt for the new upper assembly.

However if you just get a new upper receiver (keeping the old barrel) then you wouldn't need a new bolt eh?