I'm thinking a 26" will fit just right in the TV cabinet I have now in the bedroom. Using a 20" now, so more size would be nice....
For me, that would appear about the same size if you currently have an older 4:3 ratio TV. (I'm sure others are different, but after looking at a lot of TV's I found I consistently judged size by the height of the picture. When going from standard TV size to widescreen you get less height for a given screen diagonal.)
A 20" diagonal 4:3 TV is about 12" tall. A widescreen of 26" picture will be about 12-3/4". Not much difference. (Picture size. Nominally. TV manufacturers round up, & down. YMMV.) (Of course, the widescreen is about 8-1/2" wider too.)
Also, if you're trying to fit a cabinet measure! The depth, bezel width, speakers on sides, back or under the picture, all affect the physical dimensions of a TV. You may have fewer choices than you realize.... (but remember fewer choices can be good, if you like at least one of them!
Good luck.