As stated above, you can't go too far wrong by going with either a Denon or a Yamaha that is in your price range. Other receiver brands that have a lot of adherents on this site include Onkyo, Pioneer Elite, and Harman Kardon, and then at higher price levels you start to see names like Outlaw, Rotel, etc., as well as separates.
It wasn't clear if you were talking about a budget of $700 for just the receiver, or if you were trying to get more than the receiver for that. If it is just for the receiver, then you have a fair amount of good choice.
One general point that applies to Yamaha, and maybe to other brands as well, is that units purchased from some on-line vendors may not come with a warranty that is honored by the manufacturer. So, you may have to decide between paying more at a store to get a unit with full manufacturer's warranty, or getting a better deal online and taking your chances. But, the savings can be pretty substantial, and it is one way to get a better receiver than your budget might allow otherwise.
Most of the manufacturers web sites provide a lot of useful specs and features comparisons, and usually list MSRP, so that you at least have a reference to start comparing models.
