If you just have to have brand new parts to satisfy your soul, the Rock River enhanced is probably the best around right now.
Bolts? NONE of the aftermarket bolts I've seen in the past three years have been micropolished, like Colt does; so they all have sharp edges that will shave the brass off the case head, and put you at risk for having the piece crack at the cam pin hole (admittedly a rare occurance).
My solution? GI surplus carriers and bolts, made by Colt. With the armed forces changing over to M16A2 and M4 configurations, and converting a lot of M16A1s, there are a fair number of milsurp top end parts out there.
Bought five of the GI surplus Colt bolt assys last year. Tried every one of them in my four ARs. Every one headspaced just fine; four of them wouldn't close on the max guage, and the fifth didn't close on the field guage. All but one of my carriers is GI surp Colt also.
Understand, all the major aftermarket makers are buyin their internals from the same couple of subcontractors, so except for style, like the RR "Enhanced" if you buy from the major aftermarket people like Bushie, or Rock River, you're buying the same part.
Whoops, almost forgot about the fancy ass "premium" brands, like Les Baer, and Wilsons. Re them, save your money. They don't work any better than the standards[:D]