Which model of Mobo and RAM suits&give best performance for my Intel P D 2.80GHz & Intel P4 3.2GHz processor?

I have two Processors both working in different computer, one is Intel Pentium 4 processor 541 with HT Technology includes Intel Extended Memory 64 Technology(3.20GHz,800MHz FSB,1MB L2 Cache) and another is Intel Pentium D Dual-Core Processor 820 includes Intel Extended Memory 64 Technology(2.80 GHz,800MHz FSB,1MB L2 Cache).Both are working differentely in a FOXCONN 8657MF series desktop motherboards in good condition using DDR(400MHz)SD RAM(1GB for each processor).The graphics is Intel Extreme Graphics.At what extent shall I upgrade the motherboard and RAM(DDR2) ?Please guide me.Thanks a lot!