So after a year and a half of using a no-name brand (literally I don't think it even has a brand name) 4x3" tablet I bought for 20 dollars, I have finally upgraded to a Bamboo pen & touch. I bought a refurbished one on Amazon because I couldn't justify spending more on a newer/bigger one just to doodle with. It should suit me fine.
I don't actually think it will make my art any better, but I won't complain if it does.
Edit: and now, four hours later, I can actually USE it. A word of advice: Wacom and SAI do NOT play nice unless everything is set up just right. Be sure to COMPLETELY uninstall any tablet you may have used previously (seriously, leave no file un-deleted), and you might still have to uninstall and reinstall the Wacom software 3 times before pressure sensitivity decides to work in SAI.
Once it finally works, I recommend the following: cut your wrists, cry a while and then get back to work on them paintings.