Best PNG Compression Software? [closed]

I've just been trying to compress an image with the PNG image format and have had varying results from different applications. For reference, the image I am trying to compress is a screenshot of this site. Here's a download of the original image.

Here are some results I have so far in order of best to worse (original image is 239KB):

PNGGauntlet (Xtreme! / None filter) ...................... 141KB
FastStone Capture v5.3 (16M / MAX/ No filter) ............ 166KB
Paint.NET 3.36 (Autodetect) .............................. 185KB
PNGGauntlet (Xtreme! / Auto filter) ...................... 208KB
IrfanView (PNGOUT 2 passes w/default) .................... 211KB
XnView (Export / 9 / Sub filter) ......................... 228KB
Photoshop CS1 (Save for Web / PNG24) ..................... 232KB
IrfanView (Standard save / 9) ............................ 240KB
XnView (Standard save / 9) ............................... 240KB
IrfanView (Save for Web / Best) .......................... 242KB

FastStone Capture v5.3 (16M / MAX/ Paeth filter) ......... 248KB
IrfanView (Save for Web / Optimal 256 / Xiaolin / Best) ..  81KB

Some fiddling with PNGGauntlet led to the best result, although it took ages to compress. FastStone is doing something interesting, as is Paint.NET because they get their results in a fraction of the time PNGGauntlet takes to crank its magic. I've separated those last two results for contrast (see how the Paeth filter seems to be causing a problem). Note also the palletized 256-color version from Irfan: this would normally be the option I would use, but I'm testing TrueColor results here.

Has anyone else got any suggestions that can beat the best results here and can anyone explain what the filters do because they seem to seriously affect the outcome depending on the image type.

PngOptimizer 165KB in about 2 seconds.

Image quality is untouched.

I've only ever used pngcrush but it works well and has plenty of options.