Should I bother getting better iMac?

I have a 24" iMac8,1 Intel core2duo, 3.06GHz, 4GB memory. 500GB storage (currently 336 GB available).
It is about 2 years old.
I don't game, do use music software quite a bit but not professional. (Bandinabox mostly, and using an external drive for it)
I use email for small home business, I do watch movies/tv shows quite a bit too.

Will I experience a faster more pleasurable iMac if I go with one of the newer i3 or i5?

add-on to post

I would sell the current one (above)... any tips on selling and sale value?

thanks

I would keep what you have. The only reason why I would say sell...is if you needed a laptop instead of a desktop.

- Nick

I take it, that for the money and time spent, I'm sitting pretty good as it is eh?
Thanks.