You can get the 42″ Panasonic GT25 at Fry’s for $598
You can also get it at B&H for a little more money

Outside of the Video, here are the Pros and Cons of using a Plasma as a monitor

Pros:
Incredible Black Level
Fantastic 1:1 720P Scaling as well as other resolutions
Least amount of 3D Crosstalk
Power usage same as older LCDs – from 80w to 240w

Cons:
May be susceptible to Image Retention
Takes a few hours to calibrate properly
Slight high-pitched noise if screen is fully white
60hz flicker

Once calibrated, the plasma will show details you will never see on a regular LCD. Get one of these clearance models before they are gone.