In a word......no.
From what you've said already the work you do is not CPU intensive nor does it stretch the limits of your gfx card.
Looking at your spec and taking into account the work you do, I'd just install the max amount of RAM (which I think is 2gb for that mobo), replace the CPU with a faster one, (check heatsink is up to the job), and use a PCI-e gfx card, (If it's not already....you didn't spec if it's PCI-e or AGP)
It really does depend on what you want to do, you don't exactly say why you are thinking of changing anything.....do you find certain apps are running slow?
64bit apps need a 64bit OS which need a 64bit mobo. This allows you to install up to 64gb (I think) of RAM, and also use the SLI/Crossfire technology with more PCI-e slots.
I doubt that you need 64gb RAM, 32bit apps work just as well as 64bit and your spec suggests that you already have dual monitors anyway so It's unlikely you would benefit from the extra cash outlay.....including 64bit apps!
A faster CPU, (and poss heatsink), and more RAM would speed things up for a reasonable price. I'd only change the gfx card if the original is AGP, and you can spare the cost, otherwise I'd leave it.
A cheaper alternative is of course to just keep your system clean of any junk that may have accumulated over the months. Defrag the HDD and the registry. Remove any temp files, cookies, etc. Check for viruses and spyware/malware etc. All of these will increase performance considerably, and it maybe just be better (and cheaper) to invest in software to keep your system running smoothly.....as you don't seem to have any major hardware problem.
Regards.