Yamaha and Denon are the gold standard for mid-priced receivers by which all others seem to be measured. You can go Marantz, Harmon-Kardon, Rotel (pricier), Onkyo, etc., but really, they all end up being compared and, at best, coming up as equals to Yamaha and Denon.
So, just pick a Yamaha or Denon to begin with and know that you will get the most technolgically advanced system in your price range.