Hardware recommendations

Hello all!

I'm looking for a new desktop setup on a budget.

I make comics. My pages are usually around 3000x5000px.

I don't use filters but I use liquify a lot.

And various color layers and many, many layers in my work

I also use wacom cintiq 13hd.

My current desktop yields awful results. It's slow, PS crashes sometimes and I loose cintiq connection constantly.

I think this is mostly due to low ram.

My current rig is:

Intel Core2duo 2.5ghz

4gm RAM

Ge force 9600gt

What kind of rig would you recommend for my work?

Is it necessary to go i-5?

Thank you!