I'm thinking my current PC is getting old and tired.  It's developing multiple issues including:

One monitor not working (not monitor but video card - likely)

Crashing on large renders in DS, Vue 8, Cararra (2000+ X 2000+ pixels).  Does not crash on non CPU intensive applications.  Doesn't crash as often when using Reality and the Lux render engine, rendering with the GPU.

I have a Win7 Home 64 bit based system with a AMD Phenom Quad core, 8GB RAM.  Video card is a Nvidia GeForce 9400GT. 

A sales rep at Fry's told me the Phenom is not powerful enough to handle the kinds of graphic intensive applications I'm trying to do, which are mostly still scenes.  Sometimes I render larger outputs 2000+ pixels for print applications.

I used to be a gamer and used AMD exclusively for many years but am now looking at switching to an i7.  What are your thoughts?