Thanks for all responses, some useful info coming out.
@Mike/ Novatlan/ dhjdhj - Now thinking of upgrading to Snow Leopard (already have this but haven't got round to installing), Logic 9, Kontakt 4 and possibly VE Pro or Bidule. This would presumably give me access to all of my RAM as I'd be running 64-bit.
BUT - and this is the bit that confuses me - if I want to run EW Play in Logic 9 (unfortunately don't have the old kontakt versions), how would this affect my RAM usage? Would that mean that Logic as a whole would only address 4GB even though the rest of the samples are 64-bit? Alternatively, if I host the Play instruments in VE Pro/Bidule and the Kontakt and VSL instruments in Logic, will that mean that I am able to access all my RAM?
(By the way I only have VSL Special Edition is this 64-bit as well?)
@dhjdhj - I don't know, is there any reason why I couldn't use MainStage to host the plugins instead of VE Pro/Bidule?
Finally, I have just been watching a tutorial about the Kontakt Memory Server which apparently can use up to 32GB RAM. Do you know if I run this in my current 32-bit set-up with Logic 8 using up 4GB RAM if it will access the remaining 4GB to run the Kontakt instruments? This final option wouldn't cost me any money and would it mean I was actually using my 8GB RAM to its potential?
Sorry, that took a long time to write, hope it isn't too confusing. Any more advice muchly appreciated.