Well, if you want to encode DVDs in the background while gaming, then Dual core would make sense. What most people define as 'Multitasking' though, isn't
really running more than one application at once, it's merely having a few applications open and switching between them. Only one of them is ever really active at one time. And Web browsing, word processing, playing movies... none of those is very taxing on the CPU anyway.
On a 7800GT you'd be able to play FEAR at 1280x960 with all the eye candy turned up. on a 6800XT you'd have to drop the resolution and/or details to get it nice and playable - with my 6800GT I ended up playing at 1152x864 or 1024x768 with med-high settings, and the GT is quite a lot better than the XT. I do tend to be very fussy though - I demand a consistently high FPS when I'm playing. Some people are happy with it around 30, but not me
A 3500 with a 7800GT will be a
much better
gaming rig than even a FX-59 with a 6800XT. The graphics card is the real powerhouse for gaming (to a point - you don't want to go
too crap on the other components, but a 3200 or up will be fine).
There's also overclocking to consider. with the motherboard you suggest there, you would be almost guaranteed to hit 2.5Ghz with the stock cooler. bear in mind the FX-57 runs at 2.6Ghz... If you're willing to overclock by much (since you mentioned doing it with the graphics card earlier, I assume you are...) Then there's no point getting anything faster than the 3500+ really. they generally all top out at around the same. My Winchester 3200+ will happily do 2.5Ghz, and the newer Venice cores are all much better overclockers than the winnies were.
If you're really going to be constantly encoding DVDs and stuff, then Dual core should be viable... But if you're only doing one or two DVDs a week, but spending 5 -10 hours gaming a week, then you'll have more fun by sinking the cash into the graphics card, and leaving it encoding overnight, or while you're out at work, or while you're eating or something. I can encode video and surf the 'net on my 3200 quite acceptably, since 'net surfing takes so little processing power, so it's not like it's totally unusable when doing so anyway. :mrgreen: