Rear projection tv's are a good bang for the buck. You get a big picture, for pretty cheap. They're pretty much all HD monitors now, as well as widescreen (does anyone make SD 4:3's???), so they will work great for DVD's as well as TV.
Downsides to rear projections don't really outweigh the upsides. They are big, heavy, and bulky. Not fun to move! Screen burn in poses a problem for anyone into video games or Spike TV. Aparently some manufactures make the screen shift a micrometer every few seconds...but I don't know if that is true or not. Convergence is never fun to deal with, but luckily most tv's have "Magic focus" or whatnot to solve MOST minor problems w/ their gun's allingment. Screen glare, and viewing angles are huge minuses in the RP line. Some screens help or worsen these areas, but most suck straight out of the box. And the number one problem w/ the RP's is the 3 bulbs. My suggestion for all RP owners is to sell your tv while it has some life left in it, and invest in something a little more reliable, lighter, and better performing...Slimline projection (DLP/LCD Projection)
At 400.00 you would probably get an older generation 4:3 model. That could mean not as bright as the newer models, your component video (if you even get one) would probably handle 480p and in some cases 480i only. So if you got 400, save at least another 500 and get a new lower end model like an Akai for around 900.00. Look out for January around Superbowl time, they will have some real good sales.