OP: Remember that it's a buyer's market right now. That means get as much quality and dependability as you can get for your buck.
The RRA LAR-8 has a bit of history to it that pre-dates the 7.62 PMAGs by seven years. RRA originally licensed it to Bushmaster, who made the BAR-10, and one of the main points of the design was that it could use surplus FAL mags, since it was conceived during the Clinton AWB, when we were no longer able to have newly-manufactured standard capacity magazines. Nobody wants to buy a military-style rifle that takes 5rd mags, so companies found ways to fit the rifles to the mags.
Biggest issues with the LAR-8 are that it has almost no commonality of parts with the other .308's and AR10's, other than a few small parts. Handguards are different, the receivers are extremely long for a 7.62 NATO, the BCG is way long, and the charge handle is unique and long to the LAR-8. I love the bolt catch mechanism on it, but the rest of the issues are a deal-breaker for many.
I would advise NOT to buy an off-the-shelf DPMS AR15 for $599, as sales are all over the place currently with much better quality parts. PSA has sales that will allow you to get a better AR for less than that, but it looks like you want a .308 AR. I would recommend taking some more time to let the sales pressure fester, while you study more about the AR15/AR10 marketplace. You will want a lightweight, quality gun in the end.
Are you aware that there are some very impressive hunting calibers that fit in the AR15, other than .223 Remington? You are already a reloader, so your doors are more open than .223 Remington and .308, although you have plenty of components for both. The .308 AR's are pigs as far as weight goes-I've owned 5 of them, and it takes a budget and a lot of patience to put one on a diet, which involves re-profiling the barrel down to a lighter weight, looking for the lightest furniture, and increasing the felt recoil forces.
I would steer you in the direction of two other calibers that fit in the AR15, that are awesome little deer and medium game slayers:
* 6.5 Grendel
* 6.8 SPC II
Basically, you have the choice of spitting 85gr to 140gr pills from both of these at energies in the 75%-80% range of a .308, with 50% of the recoil, and from a lightweight AR15 carbine that your kids can shoot without wincing. There are scores of factory loads for both of them, lots of reloading components, and they are superb performers from the AR15 receiver set.