Just plug your SLI'ed cards to your Plasma HDTV via HDMI or VGA.
There is a common issue with connecting a PC to a HDTV where either:
1. The desktop does not fill the screen even at 1920x1080.
2. The desktop is too big to fit on the screen all at once even at 1920x1080.
You need to go into nVidia's control panel to adjust the scaling (where ever that may be) to properly fit the desktop on the HDTV.
Adjust brightness / contrast as you see fit.