So I got ATLauncher to work. (That's a Minecraft modifier pack platform. You run it, choose the pack you want to play, and it takes care of downloading all the mods and starting up the right version of MC.
Turns out I've been running 64-bit Windows, but 32-bit Java. And apparently this causes problems for some things (like all the mods I wanted before, but which wouldn't work for me and I had no idea why. >.>)
Now I have 64-bit Java, and I can get several modpacks running. So I'm thinking it may be time to set up a Twitch streaming schedule, and stream a modpack on there.
Hey, if I do a test stream one day soon, to see how ATLauncher or Tekkit play with OBS, will you come watch and tell me how the quality is viewer-side?
Yay! ^_^ It wouldn't be a long stream, just something to test how well my computer could handle all of that working at once. I really need a better computer.