So my previous computer had a Realtek sound card, even though it was also a MacBook (just a much older one)?
This is way more complicated than I anticipated. I thought getting a gift of a new computer meant I finally had a solution to my MS Extra recording slowdown issues, not cause additional recording issues. And I can't rely on the ability to keep using the old one, either, because the monitor is nearly broken.
Anyway, I just tried out Camstudio, which appears to have an option to record from speakers. Except setting it to that gave me a "WaveoutGetSelectControl() failed." error, then it still recorded from the microphone, and reverted to the microphone setting when I closed and reopened it (other settings were saved).
Additionally, it resulted in a huge file (149MB for 3 minutes, I normally expect 300-450MB for a full 1cc) which took several minutes to process after the recording stopped. I checked the compression settings but there seem to be only three available codecs, not including the ffdshow codec I've been using (which still works in HyperCam 2 verifying that it was reinstalled correctly), or even the Camstudio Lossless codec from the same site that I tried installing to see if it'd show up.