NEC 1525S LCD, Any good?

Hi guys, just finished end of year exams and decided to build a projector. Spent the entire day reading the forum, loads of great info!

I have a NEC 1525S LCD monitor, its kinda old, cost something stupid like $1500 dolars new but I got it for £10 as the backlights are sketchy!

Specs are:

SIZE: 15.4" ( 12" * 9.5" )
RES: 1280*1024

The best thing about it is the incredible resolution for its size, however this is what worries me.

I figure more pixels means more transistors printed on the screen and therefore a brighter light will be required to illuminate the screen to the same brightness as one with XGA resolution.

I have a 400W Metal Halide HIT lamp (40mm arc) do you think this will be enough for a decent iimage size of say 50"?

I'm wondering if i should use another LCD monitor I have lying about, a 1024*768 NEC with DVI input.

Which should I go for?

Also the MH lamp I have is a 10k colour temperature, not good but i figure I can just adjust the RGB values to compensate, think this will be ok or should I get a new lamp?