I will prefer an Athlon X2 3800+ as the CPU , its around 320U$D
For motherboard , Nforce 4 SLI is good , brand is your choice . I would recommend DFI nforce 4 SLI-DR if your budget is sufficient . In low range a Gigabyte K8N pro SLI or an Epox 9npa+ ultra would be fine too .
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