I like the AE900, but you will get more real (after calibration) output from another projector. The NEW InFocus projectors (IN76) will give you a much higher calibrated lumen output and will come in closer to $2K instead of $4K+ for the 7210. It is worth that much more than the AE900 IMO.
If you have ANY ambient light, including additional displays, in the sports room, then you will want to consider a high contrast and perhaps higher gain screen in that location along with limiting your screen size to get the most out of the lumens you will be putting up on screen.
For a plasma - I would go with the Panny. Yes, the Vizio looks good, but going with a well established product for a fairly major purchase is a much better way to go typically.
Finally - 42" is about right. Actually, from 14' viewing (in bed) a 42" EDTV is typically plenty of resolution for most people. Go look at HD content on 42" displays at 14' at your local store. Look at the ED model and the HD model 42" display with the SAME material playing on both and then decide if spending more on the 'HD' model makes sense.