I got a Multivision and have recommeded them to lots of people - like every company they have their good days and bad days but I like the build quality of their machines and their willingness to quote for what you want rather than you having to buy off the (virtual) shelf.
Give them a ring and they will fax you a quote for what you want.
As for the graphics card - I don't know.
If you think you can wait, then the machine will have a better spec in a couple of months, but that will always be the case. A budget of £1500 will give you a good gaming experience if you get a decent monitor and sound card to compliment the graphics card.