Ok, I love DosBox and use it with no problems, quite simply, it rocks (unless I use some svn self built versions, but that's another issue) with my simple joysticks and such, it's a great emulator (though it's still kinda icky how I can still hear the buffer after the "PC Speaker beeps"), but if you're willing to go the distance and use your Thrustmaster thingies...
Funnily enough, depends on what games you intend to run: some might actually run too fast, if they run at all, I remember trying to run digger on my old VGA 286 (yes, real hardware)...no go...so...you can imagine. (Hell speed issues are why I started using VDMSound and then DosBox a lot of years ago)
KVM switches can probably be fine, their problem is, with higher resolutions, that they tend to look like crap instead of lower ones, but still...check the specs, after all, most DOS games didn't go to a really high res. And the switch may not support it, though it would be weird. While I'm on the subject...be prepared to have a monitor that looks like crap at such low resolutions under a KVM or using a direct connection...if it works at all. Ahh lovely LCDs.
Given the fact that you're hell bent on using that old hardware, I'd say the way to go is to build a system, the motherboard manuals should have a spec and even model numbers for supported ram (though the sockets themselves are pretty, pretty clear), so you can do a quick google check against all that old hardware you have (if you have so much, I'd say you run a shop, but you do say you have no clue...so...why?): it's DRAM with no ECC and such? Maybe RIMMS? Compare the model or part number of what you have against a google search (the specs should pop up somewhere, and rather quickly) and see if it fits whatever motherboard you choose.
I don't know if your game card needs dedicated drivers, but if the floppy/cd got misplaced/rusted/eaten by a dog/eaten by Leon's mom you should be able to find them floating somewhere around the net.
If you have so much old hardware, there was a nice PCI Yamaha card...Sound Blaster compatible and kick ass midi (XG thingies=, hell, I have one...somewhere...I think...unless I sold it.
Anyway...that's what I say.