Have the REM R25, and its a good shooting rifle. It is REM rebranded DPMS. Other than no recoil pad originally, o don't yhink it was as gard shooting as modt bolts I have shot. Haven't shot the others, though so can't speak to them. Plenty of build parts though, so for that aspect probably best way to go.
And do remember it was the original design before Stoner was asked to make a children's version in 5.56.
You can then also make an upper in the various 308 based cartridges. 260rem and .338 federal look really interesting.
Re: Talk to me about .308 semi-autos
26"If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin” – Charles Darwin