If you're going to run those kinds of apps the memory can't be high enough.
4Gb is also the absolute minimum for Win7 64bit to run smoothly, not even taking in account those apps. So you would benefit a lot with more memory (PS: it's totally useless to have more than 4Gb memory on a 32bit OS though). I would say have at least 6Gb. Preferably 8Gb or even more seeing the kind of apps you want to run. (PS: make sure those apps are the 64bit versions though, this will again be very benefitial)
Having enough memory can speed up your apps way more than investing in a slightly better CPU but having not much or the minimum amount of memory.
Memory is actually not that expensive anymore, you should realy invest in that. The thing which makes it expensive is the DDR3. If your motherboard also supports DDR2 I would buy that instead if you're short on cash (it is roughly twice as cheap). You will loose some performance speed, but at equivalent speeds that is actually not very noticable.
Also:
http://www.w7forums.com/windows-7-64-bit-vs-32-bit-t484.html
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