The advantage of Dells (to me) are the many inputs. The 2007 and 2407 models all have component, DVI and VGA, and if I'm not mistaken the 2407 has S-video? It also has some cool features like PIP, very useful if you're playing X360 and want to use your computer at the same time.

But one thing I think is lacking is the 16ms response time....I don't know how much that impacts playing X360 on it....

I don't think there is any real problem. The 360 is supposed to be able to do 1080i, which res is about 1920x1080. So even up to 24" LCD should be no problem.

Definitely your 20" LCD should look awesome. I have a 19" and the graphics look great.