Assuming it is a reference model, most will be the same. The higher end models have differences in clock rates and cooling that may make one better than another. Asus can be a bit higher in price to an identical model card from another manufacturer, but they are pretty good as far as quality goes.
I don't know any stores that accept paypal in-store. You may be able to order online for pickup and pay that way. Admittedly I've never really tried to buy something instore via paypal though.
I meant to say hd7870 ............... fail. LOL
Also I have the money in paypal... and I need to use it today... I think if I want to cash it from the bank I need to way like 3 days or something U.U