You should find reasonable value in the 26 - 28" size. 30" is not that popular - 32" is more common.
I would say to stick with good brands like Sony, Philips, Panasonic, Samsung, etc. and buy the one that is the best value with the features you want. Just look for the "HD Ready" logo - not "HD Compatible" but "HD Ready".
Don't bother paying extra for features like Picture In Picture - you won't use them.