IMO if you are going to OC those Hawks up over 900mhz then it's probably not worth the hassle of returning them but if not then definitely swap them for HD6870s. Or return them and wait a month and just buy an HD6950/70 instead.
The most interesting feature of the new series is the morphilogical AA mode. I have a few games that just won't AA normally, but this new AA mode is supposed to work on anything in theory, since it requires no info from the engine and is post process.
Due to a couple of games I play, I wish I could justify a change.
Since your getting two cards right off. IMO, I would back off the gtx 470's for the cooler running 460's or 68xx's . If your gaming at 1920x1080 your going to have incredible fps in almost every game with every setting maxed.
Especially if the cards are running on top of each other, without a slot in between.
I will be playing at 1920x1080 on 1 screen.
I dont know if heat would be a prob with the SPARKLE SXX4701280D5-NM GeForce GTX 470, if its not would that 470 be a better choice?. I got a coolmaster HAF 922 case, I added a MegaFlow 200 fan to the side and I do have a slot between the 2 card.
I just got them, few days ago, so I can still get refund on them.
I am thinking of changing them for the 6870 because its the same price.
With the 6870 stronger I will last longer with them then I would with the 460 before I need to change.