which one either upgrade the old 3200mhz e4300 to an e8500 or go sli with a second 8800gts 512 and wait 6 months and upgrade the processor then??
You're good either way. I'd say go sli first. But ideally, you should just save the money and upgrade everything in 6 months. What you have now is good as is.
I'd vote waiting, but if you feel like upgrading anyway I'd think SLI would give the biggest improvement. Your CPU is already quite good already (at least for gaming).