I am thinking about trying to build an AR.  I want to start first with a stripped lower and mate it to a complete upper.  I'm not sure I trust myself enough to assemble an upper from scratch.  

I wanted to know if it makes sense to mate a high-end complete upper with the cheapest lower I can build myself.  This is minus the trigger, though, because I would put in a decent trigger.  I see all these stripped lowers right around $100 which perk my interest, but am aware that there are also much more expensive stripped lowers.  So if I build a lower using a cheap stripped lower, does it make sense to get a really nice upper for it?  Or is it a waste?  Will I not be getting the full performance out of the upper?

As for the use of the rifle, it would be for general plinking and possibly varmint/small game hunting.  If all goes well building a lower from parts, I will think about making my own upper down the road.

When I built mine I asked the same thing about lowers. The general consensus was "who makes a BAD lower" and "just pick the one with the engraving you like best". So I just went with a Palmetto State Armory lower for $70 and called it a day, no issues with it so far!

Only thing I have heard is the play between upper and lower when using different brands, most of the time you won't notice so I am told. My buddy's Spikes lower and DPMS upper mate together fine so I wouldn't expect a major issue from what you want the rifle to do.

You are on the right path. The accuracy and reliability all reside in the upper - the lower just holds the bits together. As long as it is in spec and comes from a reasonably reputable vendor, you are GTG. Just avoid the plastic lowers - aluminum only. Upper-to-lower fit is also relatively unimportant... so long as the parts hold together OK, a loose fit should not impact accuracy or reliability at all. The same for cosmetics/color match etc.

Thanks for all the info.  Seems like a good way to go, even if I don't go full into making my own uppers.

You're right where most of us have been, and I'm happyto report all that matters is your upper.  All the accuracy, and almost all the reliability, is in the upper.   loose fit or misalignment between upper and lower is a non issue when it happens, and it happens rarely.  almost everyone ends up posting a "my upper is loose" thread, and finds out it doesnt matter.

Lest I paint with too broad a brush,  it IS possible to make a bad lower, but it is very hard.  the AR really is the Lego of the firearms world.  Out of spec lowers can be made, but you'll be hard pressed to find one unless you get one made my someone starting witha  plain block or an 80% and no ability to measure or drill.  And you're not going to do that.  It's just too weird.  $100 is about what  a stripped lower has gone for for about ten years.  you should be good.

Note:  I will refund none of your money if you get a bad one

In general, the lower is not that important, but it does hold some parts that are important (i.e. the trigger).  Free float a good barrel and that is where it is at.

I have not seen a bad lower in a long time.  The last one was made in the 1980's by Olympic Arms, and appeared to have been completed by a drunken high school special ed shop class, literally.  Since it was pre-ban, it sold for $700 during the Clinton AWB as well.

Anyway, as long as the lower is made from 7075 T6 Aircraft-grade Aluminum, is machined to the correct datum, and is hard-coat anodized to a type III Mil-spec, you're good to go.  I have yet to see any standard A2-style lower that has not been made this way in years, therefore, I bought Palmetto State Armory lowers when they went on sale for $49.95 a piece, as many as I could afford.

Most lowers are actually made by around a dozen or less machine shops in the US, run in batched numbers with engraving for each end-user.  LAR in Utah is probably the largest manufacturer of uppers and lowers for the market right now, servicing several big-name AR15 "manufacturers".

You can then get into forge codes and fit with your lower after that, if that's an issue for you.  My opinion is that if you're spending over $80 for a standard lower, you're spending too much.  As soon as the specific lower offers additional features, then you can justify a price over $100, like a funneled mag well, billet, different controls, etc.

CURSE GMAIL!  Aimsurplus restocked Spike's Tactical lowers yesterday afternoon and I didn't get the restock notification email until this morning (email was sent at 3pm).  They are already sold out of course.  Called and the guy said they had 300 and they were gone with the quickness.

1st build was on a Spikes $109 from local gun show ($460 Del-ton Carbine Kit)

2nd build was on a PSA Fathers Day Lower $50 (PSA Middy)

3rd build was on a DSA Blem Lower $60 (PSA Middy)

all have worked well together....hold breath and see what Black Friday holds!  Good Luck!
edit:grammer