I have a Double Diamond Lower that takes Colt Mags, paired with a Rock River 9mm Upper. I went with the dedicated 9 upper only because it does not have the hole drilled for the gas tube. Its not a huge deal, but keeps the blowback from throwing out into the handguard / barrel. Just a preference thing.

As stated above, using Glock mags is going to require a dedicated glock lower. Double Diamond makes a great one, But I think their lead times are crazy now. Also, glock mags will also require you to 'fit' your bolt to the mags. The feed lips on a glock mag are higher than they are on a colt mag, and require you to take some material off your bolt to avoid excessive wear.

If you're interested in taking a look at one and ideas, I can meet you up at Bowers sometime, since it says you are located in Englewood.

Obligatory gun porn below...