Would it even be worth it in this situation, or would having somebody browsing the net on a desktop via wifi take away enough magic internet juice that it wouldn't benefit me much?
You can easily play video games online while someone casually browses the net. It gets bad though as soon as YouTube is turned on, that's pretty much a given. It really doesn't matter whether it's a wireless device or not, the bigger issue is the amount of packets in rapid succession drowning out your router so that your gaming packages get less priority as a result.
What you can do is you can play with setting max traffic per IP (or per MAC-Address, or device name, or w/e). This has different names, depending on the router manufacturer. It's commonly called traffic or packet shaping. Not every router supports it, some only give the option in an expert mode. Read the manual, basically.
You want to ensure a healthy baseline for your gaming device, that's really all you need. About 200kbps reserve for a console should definitely do it.
Some games go crazy with traffic though, like DayZ, for example. Keep an eye out for those. Might want to monitor your traffic and draw conclusions from that.
Note that that won't help you if torrents are going on torrents drown out the overall connection stack in a router, simply put. So speed limiting doesn't make a difference to the reduced connection quality on other services.
A switch won't really do much for you, at least not by definition. What a switch is supposed to do is two things:
Split up one ethernet cable into more ethernet cables
Act like an end point in terms of packet quality (so you use a switch if you have a really long distance between router and PC, for example, and the switch transparently negotiates erroneous packages, which yields better quality overall)
is the Sanskrit word for "instrument" or "machine"'
