I wouldn't quite say that...
My understanding with mame'ing any pc, would be to see if the video cards you have currently will work with Soft15KHz, as this will leave you a more multipurpose card.
Plan B would be the ArcadeVGA route, as the card is a modified radeon 9x00 card (I think a 9500, don't recall offhand). The reason i say this is plan b is that the cards aren't exactly that robust for newer games.
Alternatively, if you've got the money to burn, and want to be able to actually see your bios on your monitor, buy an ArcadeVGA, or in your case, a monitor with higher resolution support.
Also, maybe trying bumping your desktop resolution down to 640x480, and take a look at the fonts then.
As for your current ArcadeVGA, what's the slot type? AGP or PCI-e?
Also, what OS are you running on? XP? Vista? 7? 98se? dos? linux?