It's just basic math, and it doesn't point in your favor.

50 lumens per square foot under NORMAL flourescent boardroom lighting. No sunlight in the room which is far, far more than flourescent lighting.

You could easily need 100 lumens or more per square foot, and in a lit room circumstance you basically can not have to much light output from any projector.

The unfortunate reality is that even with 4,000 or more lumens you may find that images aren't delivering what is hoped for.

I would not make a recommendation for this without seeing the space, but I likely would set a baseline around this level of projector.

http://www.projectorcentral.com/Sanyo-PLC-XT35.htm

If you don't have the budget to do this, then don't do it. Don't waste the money on the wrong product, but put the money towards something in the future. Even with the biggest rush, you can't change the dynamics of your situation, but you can work towards it.

Good luck.