Thanks for your help, I appreciate it. However, I did already mention in the first post that I couldn't find anything regarding Wake on LAN in the bios, though if anyone can confirm for me that it's there, maybe I missed it somehow.
Router should be configured correctly. The problem is that the LAN port on my PC doesn't even light up when it's in sleep mode. I'm not so sure about the router but I don't see an option like that (Linksys with tomato firmware).