Big fan of Sony and Samsung myself. I feel that when you're looking at non-HD channels with them (granted, rare, but can happen), the quality is better.
As for Plasma vs. LCD (or LED), I hear that Plasmas are fine, if you have no light/sun glare to worry about. Where my TV is, I was a bit concerned about the ceiling canned lights giving glare, so went with an LCD. No idea if it would have impacted a plasma or not - wish they let you test one at home before buying.
Either way, HD on both types is amazing. "They say" that plasma is supposed to be better for fast motion (think: sports), but I have yet to see any faults with my Sony LCD, and I watch a ton of sports. And I'm a pretty picky b@@#$@ about these things.
proanti1 has a good point that Vizio has less expensive models that are good. Take his recommendation and check 'em out at stores to see what your eyes can see. Also, cnet.com usually does solid reviews of stuff like this. Of course they love the expensive stuff, but maybe you can read a thing or two about Vizio there (or brands to avoid).