What are you doing on your monitors? That greatly affects what we'll recommend.
If you're just doing work, and not gaming, then any recent ATI card could probably work just fine (so long as you buy one ACTIVE Displayport --> Dvi converter).
What's your current power supply?
Its mainly charts and trading software, but would like it play some games at the weekends and watch internet TV/Videos, its size of the card really thats giving me big problems as I've been told anything over 22cm could touch the harddrive
At a push I could use a combation of PCIx2, or PCI-ex1 and the PCI-ex16 slots available
Zoostorm say the PSU is 300-350watts max