I just placed my order with Magpul for one of their Collapsible M93 stocks. I'll be replacing the A2 stock on my preban Colt 6601 Match H-bar.
If Oly arms had released their AC4 Pnuematic recoil buffer for the carbine tube, I'd get that. Unfortunately, it won't be released for a while if at all.
For now, I'm looking for a quality recoil buffer and spring.
Std carbine spring and buffer is all you need for semi-auto. If running full-auto w/carbine stock, typically use a heavier buffer to control cycle rate/function of rifle.