A 990X is the cheapest AMD chipset that supports SLI, you dont really want to go for an nVidia chipset they were known to have issues so your only good options are these two boards.
nVidia chipsets are known to have issues, there is a reason that nVidia no longer produces its own chipsets for normal desktop usage. nVidia chipsets have not been recommended in a long time especially since the newer intel chipsets have supported SLI and now some AMD ones do as well meaning there are much better options.
yea, but the 2 mobos you have listed before are too expensive for me
the msi nf750, hybrid SLI only runs at x8 x8 not dual x16 but that doesnt sacrifice too much, right?
is there is any thing "much expensive ? $)
No it cannot, only the 9xx series of AMD chipsets supports SLI, and if you are spending enough to get 2 GTX 460s you should expect to spend a bit more on the board.
why is that ?
am going to get an athlon ii x3 455 which am3 cpu that will work at the xfx 750a
well it won't support future processors, it uses HT2 it doesn't have USB3 it doesnt have SATA6GB/s and XFX don't give support for that board anymore, (since it was released 2007/2008). Also it only supports AM3 processors with up to a 95W threshhold as well as that mobo having issues with not being able to unlock cores (its a bad overclocker too).
and ofcourse it runs on an Nvidia chipset (which pales in comparison to the AMD chipsets).