i have two evga 9800gt 1gb cards and will i be able to run it on 10.6.8 or even lion

and for hdd which brand will give me the least errors cause right now i tried to install 10.6.3 on amd system and i got the boot error when booting without ModCd and i had a WD green serise or Hitachi (cant remember cause i have 10hdds in my pc)
so which Hdd will give me the least problems and could this be casued by SATA III connector becasue all my HDDs are SATA3 and where can i find a good hdd under $70 which is at least 500gb and 7200rpm