If CentOS or RHEL works are are certified on a platform (built up or mobo/cpu combo) -- SME Server 8 should work.
Suggestions for thine build though if you are not Virtualising mulitple OSes on your Core i3 proposal: Get any of those Atom 510/525 based systems (dual core, hyperthreaded) -- they sip power but decent enough to run even a busy SMB SME server. They can go up to 4GB Memory only though but it should be more than enough.
But if you plan to run SME Server as a virtualized OE on a Core i series system -- yessir, Core i3, i5 would be the way to go. If you plan to run more virtual OSes (say SME Server, Windows Server, other OSes) -- you may be well off investing on a core i7-870 (95 watts peak).
I am running an AMD Thuban X6 (6 real cores versus 8 virtual cpus on the Core i7 series) - 16GB RAM system though with CentOS bare OS with KVM Hypervisor. I have successfully run SME 7.5.1 and prototyping currently updating to SME Server 8.0). My rig currently runs 7 Virtual OS Environments 2xSME Server, OpenFiler NAS, Solaris 10, Windows XP Pro (Secure Browser/VPN Clent to Office), VortexBox Music Server, Windows 7 ENterprise, CentOS 5.5 and MS-DOS 6.22
;^))