Any reasonably priced line doublers?

I'm not very familiar with line doublers, so I'm seeking advice. I've seen some auctions for Faroudja line doublers, but they are very pricey.

Does anyone have a recommendation for an entry to mid-level line doubler, the brand/model/approximate price? Do they work on existing analog TVs? Do they make a really discernible improvement?

No, they only work on tv's with a high definition capability.--Able to scan at the higher rate. Regular non hi def scan rate is 15.5 Hi def scan rate is 31.-- This applies to progressive scan dvd players also--reg tvs need not apply.Run the dvd,or sat. box cable, direct to your tv. Use as high a quality cable as you can.--Such as the Monster M2000 s- cable--available on the site(buy2;get one free)
I have had great results with the DVDO iScan Pro. I feed the satelite, DVD and VCR through it and the results are much improved. Silicon Image also offers a less expensive model (I think it is the iScan Plus V2).

You will need a HDTV capable of handling a 480p signal.
Thanks guys. I guess I need to hold off on this idea until I get an HDTV model. Currently I have a Mitsubishi 35" direct view tube TV. I have it connected to satellite and DVD with the new Tara Labs RSC S-video cables. The picture is beautiful, especially with a monthly tweaking using the Video Essentials DVD. It's just that on occasion I can see some barely visible lines when the picture contains a higher white level to it. No one else notices but me.......