I actually will never again skimp on a random lower unless I can pre-test upper fit. You don't have to spend more than $75, but through experience, a lower really is not a lower.
So my SI Defense lower was kind of eh to start with years ago. I was a dummy that was originally going to spend an extra $100 just because I thought the Noveske roll mark was cool still is, but ended up getting the SI after happening on them in a pawn shop and seeing they were made in Montana. The white oak armament upper receiver (adco assembly with DD barrel) is a standard slightly wobbly fit (total mutt rifle), but the holes were totally out of spec. I had to sand the shit out of my safety button to get it to fit and errything else took a little extra pounding to get in place. Once assembled everything is fine, just wouldn't buy another one.
Fast forward a few years and I'm building a rifle for waifu and father. I had a couple what should have been $50 wonder lowers from Delaware Machinery that my dad had bought for me in 2012 as a Christmas present from a local bubba shop and just gave him one. I wanted waifu to have a really wobble free, relatively premium everything rifle so I splurged on a whopping $70 Aero Precision because they have a nice clean roll mark and more importantly that extra set screw to tighten things up.
Both of the rifles are solid with nice ALG handguards and high end BCG's and components otherwise, but the upper to lower fit on that delaware machinery is fucking atrocious. I actually have to break it over my knee to get it to open. I have to kneel on it to get it to squeeze down enough to push in the rear pin. I break it in a little more each time I'm over there, but fuck that lower is ass. The hole for the mag release button was visibly crooked too. I tested it with multiple uppers and it is just cheap shit. It works fine for now functionally, and my dad loves the rifle regardless, but I think we'll eventually move everything over to another Aero Precision. Of all the builds I've helped with, Aero precision has always been tight, but still easy to pop pins. Have never actually used the tightening set screw.
The Anderson's look...like a lower, but I've never tried building off of one. Can't really say one way or another on those and am not really that anxious to try after those dumb delaware machinery things. Billet is usually a huge waste of money and only adds bulk and gayness.
TL:DR; Get an Aero for an extra $20 and save yourself a headache.