I have been trying out a little of everything, including using the ArcadeVGA with Mandrake Linux 9.0. I was able to get the Gnome desktop to display nicely on my arcade monitor. I had to set up my /etc/x11/xf86config-4 file by creating my own modeline. I set up the Monitor section, the screen section, and added a modeline.
The first time I got to see Gnome running on my arcade monitor, it was after I entered the following modeline in XF86config-4. I actually stole this modeline directly from Aaron's Millipede Mame pages (note that I basically have the same monitor as he does wg25k7191 vs wg25k7200):
http://sparhawk.sbc.edu/MAME/software_advancemame.htmlmodeline 640x480 13.5821 640 696 760 864 480 484 491 521 -hsync -vsync interlace
(This is the AdvanceMame modeline - I forget if I had to make any slight syntax changes to it to make it work for XWindows).
I'm basically a noobie with Linux and Advance Mame, but it seems to me that if you can get any resolutions to work in Advance Mame, then you can enter those modelines into your XF86config file, and use it as a custom resolution for XFree86. I got some REALLY low resolutions running on Gnome.
I didn't try very hard, but I couldn't get XMame to display properly under XWindows. However, under SVGALIB, AdvanceMame looked really awesome (better than the ArcadeVGA under Windows. Under Windows I always get some very minor problems, I think it might be called "tearing", but I'm not sure).
Sorry I can't explain much better. I was just throwing stuff at my XF86config file, and I happened to get lucky.