Would a second monitor significantly decrease performance?

[Technochicken]

I'm thinking of getting a new monitor, because mine is a 15 inch, 8 year old lcd. If I got a 22 inch monitor at 1680 by 1050, and used my current monitor as a secondary screen, would that significantly decrease performance on games? I have a geforce 8500 gt w/ 256 mb vram, and i would only be playing games like Battlefront II and GW. currently, i get about 60 fps on GW.

 

[Tmagic650]

The video display between the old and new displays would be very different in quality and video speed