Outside of what has already been said, there aren't any major upgrades to the 19s from 04 to 05 like there were with some of the larger units. At some point in 05 the larger units (25' and larger) got taller rock guards and upgraded axle capacities.
In the case of the 19', if it has been well cared for, and it has more options than the others you see, yes, $21k today is a good price.
I had a 19' and here are a few suggestions I would make to anyone looking for a 19'. Make sure you have at least 1 fantastic vent. 2 would be better, unless you are looking at an SE or CCD version that has better windows.
Manual hitch jack can be a PITA after a while. Not terrible, just not as nice as having an electric one.
Last suggestion is you have pets the LS upgrade pkg or if you do it yourself (it's not hard), get the screen guards for the screen door. The cost of the guards will more than pay for itself if your pet tends to play hard on the screen.
Computers manufactured by companies such as IBM, Compaq and millions of others are by far the most popular with about 70 million machines in use worldwide. Macintosh fans note that cockroaches are far more numerous than humans and that numbers alone do not denote a higher life form. -NY Times 11/91