There is no doubt that Cat5e cabling is the best option for connecting in the home for gaming and video streaming. However, unless you're a licensed cabler who can install network cabling safely (there are power cables in them walls too!), it's not an option (unless you can run under carpet etc.)
1) Stick to 2.4GHz as it is better at penetrating walls and stuff, (but this frequency is more crowded).
2) Buy a really good WiFi card with antennas, then use extension cables on the antennas to get them out of the clutter at the back of the PC.
3) Try a WiFi Range Extender. This will essentially re-transmit the router's existing WiFi SSIDs from a point closer to your pc. Choose a dual band one.
4) Try powerline network gear. You buy a pair of modules that plug into power points and they talk to each other over the ac power cabling. Plug one into a powerpoint near the router and the other near your pc. Then connect with Cat5e patch leads. Should be plug and play.
The best option depends on your individual circumstances; no magic bullet, unfortunately.
One last thing, the safety issue with doing your own wall/ceiling cabling is real. Life and death stuff. Don't do it without the training and qualifications.
The house is not ours, so wall cabling was already out of the picture. I was thinking of getting our ISP to send a team out here and install a new wall outlet for our router in my room, but that will require modifying the house and can get pricy. That option will be my last resort. I was looking into running a powerline so that I can also boost the signal to my Xbox as well, but I've been hearing mixed reviews. I think a PCI card is the next best step as I still have a final slot for it and it won't add any extra clutter to our house.