Line doubler, do I want one????

I have a front projector, and was told that a line doubler, is a "must have". The picture now is OK but not great, are line doubler's worth the $$$ and if so any suggestions. I have a Sharp XVs-55u and it shoots onto a 100" 4:3 ratio screen. By the way what does a doubler(or better) actually do? Thanks for any help :-) Tim The Tire Guy
If you haven't already, you may want to invest in a good AC line conditioner and power cord first. Then play with the contrast/brightness ratio. Since you can't get more lines than are broadcast and/or capable of being processed by your tuner, a line doubler can, at best, only do some sort of interpolation.
Tireguy: I'm not familiar with that projector, but since it's a Sharp I'm going to guess it's an LCD with a built in "doubler". I put "doubler" in quotes because it's really a misnomer. Most doublers just convert the interlaced scan to progressive scan. This increases the brightness and sharpness. If you had a CRT projector I would say you definitely need one of these unless your only source is a DVD with progressive scan--then it really isn't doing much for you. The other device of interest is a scaler. It converts the incoming signal to progressive, but not necessarily at 2x the fequency of the interlaced mode. Rather it converts it to a standard progressive output, for example 800 x 600 pixels. The more expensive scalers are capable of very high resolution and very high rise times which give the impression that the resolution is even sharper than it is. Faroudja has done an outstanding job with this--and the price they command for their equipment is somewhat of a testimony to that. Well, I may have given you more info than you wanted, but depending on the projector (if it is in fact LCD based with a fixed resolution and built in scaler) an external doubler is not likely to buy you much. If I'm wrong on the projector type and it's CRT based, then a doubler could make a sizeable improvement.
Ok well it is a LCD projector and the only source is DVD and the player I use has progressive scan so I probably don't "need" one. Thanks.