I dont see the draw for these... 2 5870's will give you the same/similar Mh for about 450 bucks
I'm thinking 6870's are the best buy at the moment. You can score them for $189 on sale and get ~300 Mhash/sec.
or just get 5830s which are widely available at around $160(no rebate/sale needed) and can also easily do 300 MH/s, or wait for newegg to get some in stock at $109