I use a video card with a DVI and an analog output. Cost just $60.
The processing power is not an issue because the video card takes over the entire graphics processing. It actually relieves the motherboard of a lot of work and frees up the memory normally used by the onboard video.
At work I use two 22 inch, 16:9 monitors. Once you have experienced multiple monitors, one monitor no longer seems enough.
Get MultiMon to support a task bar on the second screen.
http://www.mediachance.com/free/multimon.htm