Extending wires/cables

OK I decided to open my wall cutout for our tv, well found out there isn’t enough slack in some cables to do this as is, what are my best options here? The cables are for: cable tv, cat3, and speaker cables.

Extending should occur at the end of the cable, not the middle. However, the more connectors you put in the line, the lower the signal quality will be (this might not be a big deal for just adding one connector, but it’s something to think about if you plan a larger job later).