Resolution confusion

I just scored a second hand 32" plasma, a "Albatron Monivision". I have no delusions about the quality of this display, but at $200 it's all I can afford.
I've read the stickies and tutorials, and my head is spinning with all this info.
I'm trying to figure out what the correct resolution is to send this display. It works fine with anything up to and slightly beyond the XGA range (all 60hz), and actually looks fantastic, but it is overscanning a lot of the picture. At 800x600 it's within the L/R sides, but overscans the top/bottom. I guess I need a 16:9 ratio? Seems something like 850x450 would be about right?
Also, when feeding it 480p from my dvd player (which is set up to output for a 16:9 TV) there is a lot of the same aliasing I get when the TV stretches 4:3 to full screen, yet there are still black bars at top and bottom.

here's the closest thing I can find to specs for this display:

http://www.monivision.com/pdfs/pd_3231_0516.jpg

I also have a Faroudja NR series Processor (not connected) which will upconvert any signal to DVI or component, but it won't scale the picture, it will only shift and blank the borders.

Yes, we're talking about a VGA signal primarily, the issue with 480p is another can of worms.

I've been tweeking resolutions with DisplayConfigX and I seem to get inconsistent results, e.g., if I change a resolution the results seem to be very disproportionate, so there must be something I'm missing with the frequency info I don't understand.

The recommended resolutions that OS X gives look beautiful, but they are all 4:3 and either under or overscanned. I can set the display to scale the picture but it's really ugly.

I'm going to try SwitchResX using the tutorial posted here, and see if that makes any more sense.