Antec BP550 Plus 550W Vs COOLER MASTER GX Series RS750-ACAAE3-US 750W

Well like the title says which is better Antec BP550 Plus 550W or COOLER MASTER GX Series RS750-ACAAE3-US 750W.
Im building computer with the i5 2500k and i plan on getting xfx 6950 2gb now i kindof want to plan for down the road incase i Crossfire them. im open for suggestions im trying not to break the bank here. Just as a side note if i werent to SLI down the road which would be best.
Thanks