Drop to 955BE + 4gb ddr3
Hit a CFable +USB/SATA 3.0 Asrock 870Exteme3
Up to a HD 6870?
That's a great idea, no need to use a 6-core processor, the gaming graphics will be helped more by upgrading the card to say...a 6970 card
You just need to make sure the case you buy can handle it. The price on the Cooler Master HAF 932 Full tower case is about $119 now so that can handle a big card.
I would downgrade the processor and upgrade the card.