I don't have the cash, but I am pondering saving for a year or two to get into 7.62 as well.
Of all the advice, the trigger issues with the M110/Knights are very real per TACOM-RI.
Reliability
Accuracy
Weight
Modularity
These would be my criteria, and the common-receiver SCAR is front runner for 3 out of 4, and the only one with small/medium caliber conversion potentially on the horizon.
Per reviews, SCAR seems to have abnormally soft recoil compared to its peers in 7.62 as well.
Reliability seems satisfactory through testing and with current military end users, thus far.
Accuracy I can't speak of, but I'm willing to bet the SCAR is less accurate than a LaRue or other comparable 7.62 AR's.
Time will tell but the platform seems to be doing everything one could want, aside from the goofy stock and (to some) short fore end.
I think the Kel-Tec RFB is a stellar concept, and if they had spliced in a variant of the AUG barrel changing capability it would be my preference, especially with smaller caliber conversion.
Since it doesn't, I say SCAR in 7.62.