Well ive decided to just spend abit more and upgrade the main PC to handle the 5 accounts budget £300
Main specs currently:
Intel Dual core E8400
4 gigs of kingston DDR3 1333
ATI Radean HD 4900
Gigabyte GA-P41T-D3 Motherboard

So far these seem like nice options

http://www.scan.co.uk/products/amd-phenom-ii-x6-1090t-black-edition-thuban-sok-am3-32ghz-9mb-total-cache-125w-retail

http://www.scan.co.uk/products/8gb-(...-9-9-9-24-150v

http://www.scan.co.uk/products/gigab...-graphics-on-b


Not to sure if i can upgrade graphics card or not yet, something about £100 possibly