There's no telling what exactly you are looking at which makes things so poor for your setup.

What image size are you at?
Are you projecting in the dark?
What screen are you using?
How many hours are on the lamp?

Quite often a lamp is near its death and is providing half the light of a new lamp, which can really hurt the overall quality a ton.

Likewise, with lights on, and a large screen, you are asking for way to much from a 5,000 lumen projector.

Keep in mind, this is also a XGA projector with a 5 year old design, which is a bit out of date, but still, this model has solid specifications and Panasonic tends to be pretty solid.

This one caught my eye though...
http://www.projectorcentral.com/InFocus-IN5534.htm

You get more brightness, more connectivity, and WAY more resolution which could help in all aspects of your setup. A new screen would be necessary though.

Here's a list of current projectors with over 5,000 lumens and in your price range:
http://www.projectorcentral.com/projectors.cfm?g=1&hide=0&mfg=&p=5000&p=10000&w=&r=&br=5000&br=20000&ll=&t=&db=&dt=&c=&ar=&dvi=&td=&i=d&is=