I am building an AR15 with a flat top upper I was wondering if any one could suggest a good quality red dot scope.  It has probably been asked before....  There are so many brands of red dot scopes it is hard to choose a good one,  and I dont want to jsut go and pick one of the more expensive ones , thinking because of the price it will be good.   One more thing I am not completely certian on buying a flat top (after looking at the AR in the top left corner of the screen).  Thank you in advance for any helpful insite.

get the flat top...lots more optics options...trust me.  

The two most common quality red dots are the Aimpoint, and the Eotech.  

There are less expensive "civilian" versions of the Aimpoint, the Comp C, and of the Eotech, called the Bushnell Holosight.  

You can save a couple of $$ if your budget it tight on these with no loss in quality, but they're not *quite* as rugged.  You can mount these to your flat top right out of the box, and there are more robust mounts available by ARMS, and a few other companies.  

I won't tell you which is better, there is a tacked post of about 10 pages where people are talking about that...I have both, and I like them both.  

The Tasco ProPoints are pretty good, I had one of the Propoint 3s, and it had the brightest friggin' dot I've ever seen.  I sold it with a rifle, so I didn't really shoot it much, but I don't think it would have had any trouble with the negligible recoil of an AR.  

I've had $30 BSA red dots on several of my rifles, and they held up well 'til I could afford something better.  

If you want "the look", you need to get an Aimpoint Comp M, or ML, and one of the Eotechs...those are the military issue type sights, and they would be mounted usually with an ARMS mount.  (The Eotech doesnt' need a mount, it is mountable out of the box).  

Poke around here, and check out the threads that have pix...you'll find a setup you like.  

For me, the simple "no fuss no muss" solution is a Holosight/Eotech on a flat top with an ARMS #40 backup sight.  You won't need anything else to have a good red dot, with co-witnessing back up iron sights (BUIS) should the red dot shit itself.