I don't think I'll ever buy a factory SA rig unless someone comes out with something completely proprietary that has benefits you can't match with some machining and light 'smithing. To that end....
8.2" 300 BLK on AXTS lower, NorthTech Defense upper:
8.5" .458 SOCOM on KAC lower and CMT upper:
12" POF 308 Win:
11.5" 5.56 Noveske Switchblock with BCM KMR on San Tan lower and YHM upper:
18" 6.5 Grendel on Noveske lower/upper:
7.5" 5.56 on Seekins upper, Northtech upper, w/XLP piston conversion kit and milled out KAC URX4, WOA Wylde 1-7" twist:
It never ends. It's all about making your rig exactly what you want/need it to be based on the application and context of the task at hand. Options are seemingly endless....