Good news everyone: it is now possible to run SF5 in full 320x200 VGA + soundblaster glory using DoxBox!
I have made some experiments on how to get the game running on DosBox, and luckily it is quite simple.
To make the game run at all, you need to up the memory allocation of DosBox from default 16 megabytes to at least 32 megabytes. This can be done by modifying the memsize -setting in the dosbox.conf file.
The other issue is the funky Soundblaster-compatible audio system that SF5 uses. The sound works by default, but you'll get horrible static and occasional crashing on exit. To cure this, you must select "emulation compatible" mode from the SF5 setup screen, and make some adjustments to the mixer settings in the dosbox.conf file. Here are the mixer settings that I used on my home computer (Intel Core Quad 2.4Ghz + Vista 64):
A fully featured dosbox.conf that I'm using to play SF5 on my setup is available here
Special thanks go to Eetu Jalonen for bringing this to my attention.