Well, there's been some developments on my requirements side of thing's, I've been talking to some of the guys on the Adobe forums and they seem to think that more Ram might not help as much as I'd hoped, what may be more beneficial for me might be an SSD raid array.
After effects is an odd app, being a 32 bit app it can only see 4 gig, the way After effects works around this is interesting though, for rendering it actually opens multiple instances of itself and uses these extra instances to quicken render time, very clever I thought, this is where having a lot of processors adequately supplied with Ram is of a real advantage (Rendering).
However there's another factor, that is the file sizes, HD video formats Bluray etc are huge, a ten minuet (Uncompressed) HD video clip easily runs in to the 50 gig region, when handling these kinds of file sizes an SSD based system is surely going to provide major advantages and with read and write speeds of relatively cheap SSD raid arrays hitting 2 gig per second, they may be more beneficial to me then simply adding more ram.
Funnily, providing After Effects with more Ram does not increase the amount of Ram preview (Video you can actually view within the app) the time it takes to load video is increased but not the overall amount it can work with. presently After Effects can only hold 1.6 gig of video, this is where I had hoped to see a major improvement in the apps performance, sadly the only improvement adding more ram to my current system will be in rendering and previewing speed, something that I can improve upon by simply installing a faster processor, moving from a dual core to a quad core will half my rendering/previewing time which would help a great deal.
So, I've decided to take this upgrade down a different rout, a new processor will help a great deal with a great many things withing After Effects and an SSD Raid array (should) help After Effects handle these huge video files, I'm still not sure about which Processor to go for but, I think I'd like to stick with something like a Xeon, that's tried and tested, I hear a lot of people have had problems running After Effects with the new i7's.
Thanks for your recomendations all, I find PC hardware a real nightmare to deal with, fingers crossed this new system will help a lot and cost quite a bit less than swapping out the mobo - adding the new Ram, and forking out for two processors.
Again, thanks guy's