Thanks for your input David. You're not the first who's emphasised the importance of Ram - definitely going to have to learn to upgrade it when the time comes. The imac is the most likely candidate for me so far here's the URL for anyone else wanting to to assist:
regarding Ram these are the details it gives:
4GB (two 2GB SO-DIMMs) of 1333MHz DDR3 SDRAM; supports up to 16GB
Doesn't mean much to me at this moment but if i'm to spen this much on a computer, I'm sure I will learn!
I'll definitely sleep on this before making a decision though.
Wow you've played with Burt Bacharach! Great list of recordings there.