mine isn´t very high end and kinda old but it gets the job done: i use a samsung sync master P2770 at the moment. it´s a 27" as you can figure by the name;)
it´s ok and very reasonably priced but the picture quality isn´t outstanding (wii looks pretty nice on the "small" screen though i must say). i will definiteley get something else with the next gen....but it really is good enough for me. soundwise i use sony wireless headphones. forgot how those are called but i do not like them too much anyway. they lack some punch/ bass. will someday look into something different there too.
27" is the best size for my set up. we don´t have a tv in the living room. i game in another room, i have my samsung mounted on a wall with a little antique desk and a cozy and slick late 60´s chair in front. all shiny black, white wall, red carpet on plank flooring. all my consoles are hidden in a white cabinet to the left. and i have a lot of plants there too, oh yeah, and super sized mario and a luigi figurines and my dog has a place there too...you can figure by the warm words i am having here: i LOVE my gaming cave. (only thing i don´t like so much is that my dog is getting old and farts like a champ - glad she has another place in the house where i can doom her too if i am getting to close to a coma).
the samsung only has one hdmi so i use a splitter, one which switches automatically. works really well. i have a ps3, 360, wii and a mac mini connected to the monitor,
i personally started to prefer the "desktop" setup. for this 27" is absolute max though imho. everything bigger isn´t working so well. i have tried many options, i would rather go smaller than bigger for that kind of setup.