First get a copy of IBM's PC-DOS 7.x
there is extensive info on the net on how to make a multi-config config.sys/autoexec.bat in order to skip using bootdisks for different memory requirements. A menu will be displayed on startup, which will allow you to select the configs u make...
I recommend PCDOS over MSDOS, because of its better tools, and better memory management.
As for sound, go for an ISA sound card, preferably a SoundBlaster AWE64. You need ISA, as some older games poll for interrupts there...
For VGA, just get a pci one, or if u can get , a PCI voodoo3 card... no probs there
ask me, I am a DOS-kid