I work for a State agency, and we get a great deal on Dell systems purchased for personal use. We get the Higher Education pricing, plus a further 10% off. Essentially, we can get a $12-1400 system for about $900.
We have owned a Dell Optiplex at home for 3+ years, and despite all the abuse we've poured on it it functions fantastically.

So, I'm more than happy to get a new Dell system. I simply can't decide, and hoped some fine Dell customers can help me decide. Questions I have are:

Is there going to be a functional/realisable difference between a dual core Intel/AMD processing core?

What real differences are there between the core available systems: C521/E521/E520 we can choose from on our plan?

If what we want as core material is 250GB HDD; 1GB RAM; Dual Optical Drives (it's for a video business, we want one to copy directly from the other) does that help any?

I realise this is something of an openended question. But this is a system we want to operate as the centre unit of a small business, and though cost isn't an issue at these prices, the aggravation of a system that's not meeting requirements could be. We want to be sure the system will do what we want, and be reasonable in its performance. The three options at Dell all seem pretty much the same, so I wonder if I'm missing something other than to get the one that holds the hardware we want, at the cheapest price.

Thank-you, in advance, to any and all who help us out!

Let's see... Processor speed will depend on what you need to do. Core2 Proc outperform just about every AMD X2 right now. AMD tends to be cheaper right now though.
The C521 is the slim version of the E521. Both have AMD procs. The E520 is the Core 2 version of that desktop. Aside from the processors, there is very little difference between the two systems.

If you end up going with the AMD base then make sure you get one with an X2 processor. Specifically the 4800+ or higher. While Core2s may perform better, AMD's procs are still very good and unless you plan on gaming(not recommended with those video cards) you won't see a whole lot of difference.

As a side note, I would get 2 gigs of ram to allow Vista to run smoother when you upgrade from XP.