I am starting to build my first 308 AR.  I have all ready purchased an Aero lower in tactical peanut butter.  I am planning on getting a matching Aero upper.  I see that Areo has to flavors.  The standard M5 and the M5E1.  Has anyone made an AR using the M5E1 upper?  I am familiar with making AR15 but I am not sure how well the enhanced version would be beneficial over the standard method.

If you use the Enhanced version, you are limited to using the fatter profile Enhanced handguard. There may be other handguard manufactrers that make one to fit  but I am not aware of any. Their regular version receiver will take their slim profile Atlas handguard, as well as any handguard with a DMPS high-profile. Midwest, SLR, and Odin Works are a few of the manufacturers that make those. You can also mount the Enhanced handguard to this regular receiver, but you'll need the special barrel nut and possibly shims to correctly time the nut to fit the handguard correctly. The Enhanced receiver does not have this timing requirement, just install the barrel and use the special tool that fits the barrel nut to the proper torque value. It boils down to which handguard you want to go with, slim profile Atlas (or aftermarket), or the Enhanced. It may also boil down to your barrel profile. If you get an overly large OD barrel, the Enhanced may be necessary due to clearance issues with the gas block.

I have built a couple Aero M5 rifles, using Faxon and Ballistic Advantage barrels. I used the Atlas handguards and had no clearance issues. I have not used the Enhanced version handguard, they delt too large in my hands when I compared them side by side at a gun store near me.

Thank you.  This is what i was lookin fer.

Yup, no worries.

I use the fatter M5E1 "Enhanced" handguard for my dedicated precision set-ups, with the special-snout M5E1 Enhanced upper, it isolates the handguard from the barrel nut.  This handguard also provides ample clearance for gas blocks: e.g. I've used a clamp-on 0.936" adjustable gas block with this HG with no clearance issues.

I've read that the M5E1 Enhanced is referred to as a "BAR" mounting system. Here's another company that makes handguards to that spec.
https://www.sgtofarms.com/product-page/sgt-of-arms-ar-10-17-arca-handguard

Unless you are bent on using another brand for handguards I would go for the Aero Precision M5E1 along with whatever Aero Precision  M5 (.308) Enhanced handguards that work for you. It makes assembling an upper receiver MUCH easier. I've built a .308 using a M5E1 and a 6.5 CM with the same M5E1 upper with excellent results. All you have to do is screw in and torque the barrel nut with your barrel and gas block and tube installed, install your muzzle device and then just slide on the AP M5 (.308) Enhanced handguards of whatever type and length you chose and tighten the 8 screws and your done OR you can just purchase the complete upper already assembled!

I've done several Aero enhanced upper builds including two of the large frame variety.  I like that my handguard as well as the clip-on NV, laser, and bipod attached to it are not directly in contact with the barrel nut.  Whether or not that is of any consequence or just my perception is unknown.  Two precision-oriented guns assembled w/ enhanced M5E1 components have proven to be extremely consistent out to 1,000 yd.  The fact that they are extremely inexpensive is just icing on the cake.