I Love my Viewsonic VX922. But it's a 19" and you want a 21" for your standard PC. The 2ms response time may be marketing hype, but I can verify I've never had ghosting or blurring.
I had a 21" CRT, so the 19" LCD is the same screen size. I don't think I need a bigger one.
You can get the 922 for $285 (incld shipping) at Newegg. Where you live you can get it at Frye's. Some stuff at Frye's is cheaper than Newegg, some more expensive. But it is nice to be able to take stuff back for instant credit/replacement if it dosen't work.
Unless you have rambunctious kids who like to poke things with their fingers, you don't need a plastic cover. If you want a little extra protection from dust and the occasional smudge, just tape a piece of overhead projector plastic film over the screen.