Thanks to all the responses, the new system has finally been ordered. Its a little different now that I've had time to research what was required along with the advice from here. I even looked at the Mac range, but they are totally over priced for what you get, so ended up getting another PC.
I went to a local store and looked carefully at what was required and found that I didn't need the quad core systems or the heavy duty graphics cards as you chaps had pointed out.
The system will be complimented with a 2 TB NAS storage system when I get round to ordering it. The old system will be reconfigured to be a storage system for the time being giving me a total storage of 1Tb on the old system and .6Tb on the new.
I bought a Dell system - specification below:
Base
Intel® Viiv™ technology - Intel® Core™ 2 Duo E6750 processor (2.66GHz)
Memory
3072MB 667MHz Dual Channel DDR2 SDRAM [2x1024+2x512]
Monitor
Dell™ 22" Black Wide Flat Panel (E228WFP) - UK/Irish
Video Card
256MB nVidia™ GeForce 8600GT graphics card
Hard Drive
640GB (2x320GB) 7200rpm SATA Hard Drive - Dual HDD Config
Floppy Drives and Additional Storage Devices
19-in-1 Media Card Reader
Microsoft Operating System
Genuine Windows Vista® Home Premium - English + XP Pro
Optical Devices
16x DVD +/- RW Drive
Video Editing
IEEE 1394 PCI Adapter card
TV Tuner and Remote Control
Integrated Hybrid (Analogue/Digital) TV tuner PCIe x1 card and Dell™ remote control
Roger