i doubt Crossfire scales better then 2 GTX 460s do, at 1920x1080 u get double frame rates compare to a single card. however GTX 460s will only go 2 way SLI.
u have to remember WoW doesnt support SLI/Crossfire so im talking about other games and benchmarking softwares
for an SSD HD, yes it will not have any impact on FPS, but everythting on your computer will work smoother and load alot faster.
Processors have evolved about 400x since the 1st intel CPU was released, HDDs evolved only about 3-4 times. in 2 decades! SSD is a massive leap.