LCD edges it in practical scenarios.
Samsung are excellent units, but do use the recommended settings founf on line (e.g. avforums).
I am surprised that some on here think that digital trickery such as image enhancement and sharpness settings can do any good to any picture so turn them all off!
And seperat component might edge over HDMI....if you could find a true HD component source in the first place (and even then its VERY questionable).
And why bugger around ever feeding video through an amp?
Only advantage with in hdmi amp i could see was it saved selecting your sound source to match the video.
Idea being, 1 hdmi cable to tv, then plug all else into the hdmi amp and select your single source from there. Audio and video is then selected at once. Much like the old media box's on previous pioneer panels. Also means you only need one socket to cover all eventualitys on the tv, an hdmi socket.
The onkyo hdmi amp i tried, was flawed though as it claimed to upscale, but it did so to a level lower than the picture quality i already had, and its menu was displayed in 4by3, not wide screen. So half a step forward and 5 steps back imho.
Lcd v plasma? I've yet to see lcd beet plasma re picture quality on comparable panels. However lcd is a good bit cheaper to make, if inferior slightly in quality to plasma. No experience of LED, although i hear its so vibrant as to be unrealistic, only what i hear though.
You will never get a real opinion until you mess with them in real life.....always ignore what you see in a shop!.
When I bought mine I spent over an hour trying settings on plasma and LCD panels and could get a better picture on an LCD every time.....it also REALLY pissed the shop staff off as I then went and bought it on line 
Indeed, when you FULLY understand the technology and how its driven and works you will soon appreciate how LCD can always win out over plasma.....you cant consider just the pixel technology alone. 
Nah, sorry. I played and demo'd till blue in the face before buying. I knew what i wanted straight out and tried very hard to buy something else, could find nothing better for under a grand at the time, 2 years ago though so it may well have changed by now.
Every lcd even the top range stuff had a net curtain picture, like the sharpness was too high, but it didnt have a wide enough scale, all or nothing. Just could not tune it out. Uneven back lights as well.
I bow to you knowledge of course, it does get warm.
But as you'll recall i did mention lcd to be an easier and therefor cheaper technology. Trouble is, for me, it shows as cheap all to readilly in the picture.
I also know someone who bought a sony lcd and curses it as being a worse pic than his tube in sd for the same size screen. Settings most likely there i guess or hes watching through a scart or rf cable or something daft.
Anyway, for me at the time, it was plasma or stay with the tube. No question about it. :-)