Re: SPS-T AAC:SD vs 700 5R in 308
I would guess that they're equal in accuracy potential. I've had a 5R and an XCR Tactical, and they shot the same, around .5 MOA with handloads. Slight accuracy advantage to the convententionally rifled XCR, but it could have been the stock fit for me. I agree with the above statement that the 5R stock sucks. It just didn't fit me well, the wide grip was grapefruit-esque. The 5R was much easier to clean. Haven't shot an SPS, but having handled them I'm completely underwhelmed by that stock as well.
If it were me and I was planning on running a can and replacing the stock I would go with that threaded 5R that pyplynr linked to. Do some shopping on stocks, find one that fits you well. I'm waiting to see the Eberlestock chassis before I do anything else.