if u wish to spend $100+ dollars for a 20% increase in render times, which is barely noticeable and its probably the best increase you will get, by all means go ahead...your better off looking at core count than u are at architecture when it comes to rendering. also got to keep in mind that ur wallet may not have over $9000 in it (just saying) although i will tell you, the quality of work you produce wont change much. i've seen awesome, realistic renders done by people with pentium 4 processors and the like.
i think that last question really sums things up for the original poster. Yes, an Athlon II x4 can handle 3d applications as pretty much any processor being sold these days can.
Regards,
NFSC
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I am currently working on a lot of secretive projects for animation sequences for videos me and my friend are making
CPU Core i7 930 @4.2GHz
Memory 6GB Corsair Dominator 1600MHz
Graphics Card EVGA Nvidia GeFroce GTX480
OS Windows 7 Ultimate x64