Noveske makes a very cleanly finished lower with a flared magwell for faster mag changes. You're definitely getting quality for the extra cost. BCM makes a great lower as well and uses a top notch milspec LPK. Both offer blemished lowers at lower cost which basically means someone else put the first scratch on it. You will too sooner or later so as time goes on the blem doesn't matter much. As Mike said PSA makes a quality lower as well so there's nothing wrong with going with them either.
There are a couple other things to consider. If you really like a certain rollmark I say go for it. An extra $50 or so doesn't matter much when you consider the cost of the entire rifle, so why not have what you want. There are some lowers I would not use even if they cost $50.
The other thing, if you ever may sell the rifle you'll likely get more with a recognizable rollmark like S&W or Colt. Also you're likely to get more money if the upper and lower are the same brand.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek