Different brands have different stock clocks. I would get the one with the highest so there is no need to OC.
Well if possible i would go for same brand as your motherboard just seems like an good ideer from my point of view
i allways go for asus boards and asus graf
^ This. Get the highest factory overclocked and good warranty card.
Sapphire tends to be the cheapest and they are very good cards(quality etc) so i would recommend that you go with Sapphire
Well just take a look at the review (those on newegg are usefull). Some of these have bad stock cooling so you can't. Sometimes the highest stock GPU have the worst sound and can be anoying. usualy you can't go wrong with asus and gigabite but sometimes the extra $ for these brand just not worth it.