I understand that an LCD monitor when not in its native resolution does not look as good. Just how much difference is there? I am not a gamer, not into video, so it may not be an issue. My trusty NEC 21 inch monitor is well over 10 years old, weighs 80 pounds. I need to downsize so I can more easily move things around. I plan to find a store that sells the monitor I am interested in and see if they will oblige me with a demonstration.

It depends on the monitor, though a regular and very trustworthy member of this forum says that newer Samsung models are very good (if not the best) at running non-native resolutions while maintaining high image quality.

My Super P3:
Pentium III-S 1.4GHz @ 1.5GHz, 512K L2
X800XT All-in-wonder, overclocked to 580/600.
250GB HD
2 gigs of PC2100 RAM
QDI Advance 12 mobo, this baby rocks!
SB Audigy 2

where i worked recently we got some new dell 17inch TFT screens.these were used only for office work. On the native resolution the text was a bit small for general use when on telephone etc, and when the resolution was changed to 1024 x 768 which everyone there agreed was about the best size to do their work, the text was noticeably blurred by the screen trying to work to a non-native resolution.
I was not impressed. Nowhere near the sharpness of image as a CRT monitor.

well, actually 1024 x 768 as desktop resolution works best on 19". 19" is just right.