Thanks for the interesting comments. While I appreciate the feedback and suggestions of other (lower cost) machines, this is between a PC and the Mac Pro for the following reasons:
1. The Core 2 Duo - I built a computer 2 years ago with a 2.4GHz Core 2 Duo processor in and had it overclocked to 3.4GHz for most of the time. I don't want to be replacing that Core 2 Duo computer with a less spec'd mac mini or a similar spec'd iMac.
2. The Mac mini and iMac are both not expandable enough for me - They both use laptop parts and therefore are very limited in what can be upgraded, and how much those upgrades cost would be far higher than other options.
3. The need for dual displays - The adapters on the Apple website are called 'Dual Link DVI' which are for using 30" Displays which currently require this type of connector and it's not to be mistaken for 2 seperate DVI connectors. (The only other option would be a Matrox DualHead2Go but not keen on that idea).
4. The screen on the iMac is glossy! (enough said about that one

)
5. With the Mac Pro I can house a number of hard drives in the case itself which saves having several external hard drives lying around. I will then only need 1 external for 'emergency use'.
However, I think the lure of OSX is going to win but as it doesn't look like the Mac Pro is going to be updated until March/April time, I am going to wait and see what Macworld brings, then if no Mac Pro, I have decided to buy either a Mac Mini or an iMac which will be used as the business 'office admin' computer and wait it out for the new Mac Pros.