Yeah, I played around with EQ settings, opening closing the EQ window, standing on my head, etc... and the sound seems back to normal. I have no idea if the few restarts I did or messing with the EQ did anything, but bass is back to normal on left channel. Other people have same issue on Apple Discussions, so there is def something strange going on. Glad it's fixed for me. I will be doing a clean install this weekend, so hopefully any nagging issues get resolved.
Only major issue for me now is that Preview no longer displays images at retina resolution, like 10.8 did (I have a 15" rMBP). If I take a screenshot and view with Preview, it will show 1:1 in retina form. But if I take that image, then save it in say Pixelmator, Preview now shows it not at retina, but double-size (pixelated). All my images in Preview do not show Retina sizing. But Pixelmator still honors the retina sizing.
This goes for every image I use Preview to view. 10.8 Preview shows them at retina resolution, 10.9 blows them up 2x. Hopefully an easy fix, as I use Preview to preview my retina images before I upload them for the web. I'll have to use Pixelmator to preview them until this is fixed, or maybe it's the new feature. Maybe Preview for 10.8 was incorrectly showing retina images?
Bryan