4650 vs 9500

Are you sure you want either? The 'Egg has a nice 9600GSO for about $40 with rebates.
Otherwise bear in mind both cards come in two flavours: DDR2 or DDR3, obviously the DDR3 cards are faster, so check the specs very carefully before making a decision.
Overall the HD4650 is faster if you compare the cards by memory type and would be my choice.