Right now I have an AMD Athlon(tm) Dual Core Processor 4200+, 2211 mhz, 2 cores (2 logical processors).....Now I was first wondering if the AMD Phenom X4 9700 2.4GHz, 2x2MB, 2000MHz FSB Quad-Core Processor is the best there is. And if i got ONE of these, would it be better than the two i have as of right now? thanks ahead of time for anyone willing to invest their time in my question.

I would suggest that you wait for AMD to sort out the erratum issue with the Phenom processors. When they have sorted that you might want to consider the Black Edition of the Phenom. However at this precise moment in time I would not suggest going for a Phenom. Dont get me wrong. I love AMD processors, they are the best as far as I am concerend. But the first release of the Phenoms leaves a little to be desired.....

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The erratum issue is not really an issue at all and I have yet to read any where on the web where someone has actually been affected by it. It is only a probable problem in virtualisation, which desktop computers do not engage in. As to your question, you are basically moving from a 2.2GhZ system to a 2.4Ghz system. Not much of an increase in performance and the reason for this is that there are not many (if any) software programmes (and NO GAMES) that are programmed to handle four cores simultaneously.
So, at this stage I would suggest that you stay with what you have and then, come beginning of 2'nd quarter in 2008 see if there is a chip that gives you a greater increase, say to 2.6Ghz or (even better) 3.0Ghz.
That is just my two cents worth!