I did already buy the stuff, but if something were totally out of whack or incompatible, I could still return it for a refund.
I guess I was most concerned about my PSU's 600 watts' being powerful enough to carry the load. I wonder if it is powerful enough if I added a 2nd 5870. Well, that won't happen this month nor will it happen in 3 months, but I'd still like to know.
I bought from Fry's, so there was a certain limit on availability which determined what I would buy. I know about Tiger and Newegg. Fry's had this now, so I could build the system now.....not next week with mail order nor did I have to worry about RMA issues. Fry's tested the MB, RAM, and CPU to make sure they worked properly for $10. I felt that was worthwhile because I live 70 miles from the store.