New build Questions

Hello - I'm building a new machine and had a couple questions regarding hardware. I will be using the machine all day as I work from home as a graphic designer, photography professional (raw photo processing) and I want the ability to use it as a small entertainment center for HD television/movie viewing. The setup will have a 24" monitor, but I also want the ability to hook up my 20.1" without seeing a performance decrease while heavily multi-tasking.

I've boiled the hardware down to the following.

CPU:
Core 2 Quad 2.83ghz v. 3.0ghz
link to newegg comparison of the two:
Newegg Comparison: Core 2 Quad
**my question here is 2.83ghz v. 3.0ghz; is it that big of a difference? and, multimedia instruction; one has it, the other doesnt. what does it mean?
**also should I consider a core i7 setup instead? i'm not sure if this is necessary for the price increase. thoughts?

Memory:
6GB DDR3 1333 or 1600

Hard Drive:
74GB 10000 rpm (for OS and Apps)

Video card:
DDR5 1-2GB, dual dvi
*If i want both monitors, is it better to go with dual GPUs? or will the one DDR5 handle both well?


I didn't include the motherboard, bc i will simply match one that will handle the hardware mentioned above.

Thanks for any opinions/thoughts!

JP