The E8400 will beat the Q8200 hands down in any application that isn't able to use the four cores of the Q8200. Mostly graphic designing and video editing would generally mean that the advantage of the Q8200 would primarily be when encoding video or rendering. I would say that overall you would probably have more use for a E8400 right now but as software gets better to utilize multicore cpus the Q8200 might last longer.
When it comes to motherboards you should probably pair either cpu with a P45-chipset based motherboard. If you don't need any particular 3D-graphic performance the G45 could also be a wise choise with its built in graphic card.
Despite what you cpu you choose, remember to go for at least 4GB of RAM (2x2GB) and at least two harddrives to match your processing power. Go for a 64bit OS for best performance with 4GB (or more) of RAM. For example Adobe Photoshop CS4 come as a 64bit application and it will happily use all that RAM.
Dear Murli ,
Regardless of talking on processor , i must suggest you to find out the right machine . I understand from your quote that you need the machine for high end graphical applications . Are u planning to have an Desktop or a WORK STATION ?? Your nature of job will be 100 % satisfied by choosing an right Work Station .