Well folks, I've found the next lens I want to invest in.
This is the Canon EF 50mm 1.4 USM. And it's perfect. I would "ask" for it for Christmas, but I want to be able to actually use it over the holidays (after having some time to get used to it), so I'm hoping to find a sweet Black Friday deal this weekend. The sample images I've seen from it online are just heavenly.
For example, this one, taken from the customer images page on the Amazon page for the lens:
I think that's all that really needs to be said.
I am always complaining that I can't take good photos at Christmas when we're all in Gran's living room opening presents. And that's because the living room is lit with warmest light from six different not-very-bright lamps all joining forces. My photos from past years are almost always blurry and not well-lit. Almost every single person who's reviewed this lens says that it's great in indoor, low-lit situations. That's exactly what I need, which is why [I guess] I'm willing to shell out the $300-something it'll cost for it.
Crossing my fingers for a sweet Black Friday deal...