I have a friend with the gigabyte ga-h77n-wifi motherboard and the default wifi antennas for the board are pretty average. I'm looking around for him to find something that would fit. Not being able to see the board I can't tell what size they are etc.
They don't even bother listing the 2.4 GHz loss, it is so bad. Remember that 3dB loss = 50% of the signal lost. Flexible, thin coax simply can't carry 2.4 GHz and 5 GHz signals efficiently. (I don't know why mfg's use it).
I chopped it off and replaced it with bog standard RG58 50 ohm marine coax and got a noticeable improvement in signal. Even though RG58 isn't ideally suited, it is less bad that the thin stuff.
If your mate is a gamer, or pushes big files over the network, and the physical situation allows for it, talk him into using a CAT5/6 cable. That's what we did in the end, and it was so much better than a shonky wireless signal.
Edit: Also, don't forget the Wireless AP antenna. If it has external antenna connectors, you can improve the signal strength at the client by fitting a high gain antenna to the AP. You can get some highly direction panel/yagi antennas, and a pair of those pointing at each other will make a huge improvement over omni directional antennas.