Yeah. I have to agree there. A hundred bucks ain't gonna getcha much.
Even if you end up using fre software synths (there are some really good ones out there. Crystal, Minimoog VA, ARP 2600 VA, ZingerDX etc) you will still need some sequencer/audio software, an audio card and a controller. In case if you own a PC (unless of coarse you own a few Macs like I do) software like Cubase A or Sonar will do fine. Not cheap at all but wirth every penny. Audio cards that come with PCs are okay but you will need a good ASIO driver to handle latency and so on. Although don't quote me on that because I do not use anything that runs on Windows XP.
However, just for messing around and exploring software synths and instruments you'll get away with almost any soundcard.
Controller is a different story. I owned quite a few. Still have a DX 7 BTW. If you can find one of those with either E card or SER-7 updates it wil serve you another hundred years or so. Even if it is banged up and scratched like it's been hit by a truck. DX is probably the most reliable and cheap controller out there. Mind you I like to program those too. BUt that is a different story my friend. Will get back to it another time.
Anyway, I think I posted a thread or two on all known MIDI controllers so just do a search. I've described and provided links for almost any controller there is. Should be in archives unless this big hard drive crash that happened last year wiped all of my writing out.
If you don't find much let me know. I'll have to type it all again.
-ED-