RAM configuration for Dell PE2950
Sorry, but it won't work. The PowerEdge 2950 can only operate with 2, 4, or 8 DIMMs. Adding 2 DIMMs won't help you. You'll need to add 4 DIMMs or upgrade the ones you have.
Reference the PE 2950 hardware owners manual page 89 and 90. You should have DIMMs currently in slots 1,5 and 2,6.
http://support.dell.com/support/edocs/systems/pe2950/en/hom/pdf/hom.pdf
Also see pages 137 and 138 for the locations of the DIMM slots and the numbering of those slots.