Vortex red dots are great. I had a Strikefire on an AR for a long time, and it served me very well. If I got another red dot (I moved to a Bushnell 1-4x PCL Throwdown and I'm loving the 1-4x life), then I think I would get a Sparc. It's lighter, and all one really "needs" in a red dot.
You have a few good budget red dot options. Those include Primary Arms, the Bushnell TRS-25, and Vortex. I'm partial to Vortex mostly because of the push button controls. Quality is similar for all of them, but the Vortex feels the most solid.