I don't know what kind of router you're using, frequency band, etc., but here's some general advice...
Get a wifi analyzer and have a look at the wireless topography in your area. Many people are still using the 2.4GHz band, and there are a very limited number of channels to broadcast/receive on (11-13). If you are in an apartment complex you can have 60 routers in range that are all using channels 1, 6, and 11 and get a perfectly good signal by switching to channel 9. You may also find that where you're set up (60ft away) you have a straight shot to a neighbors wifi (through a flat wall or window) that is on the same channel causing data collisions.
Free wifi analyzers:
You can change your wireless channel from the router configuration page in the same area as you set your SSID.
If you're connecting over the 5GHz band you can try switching to a different channel as well - trial and error or using a 5GHz analysis program...
If troubleshooting your connection in this way doesn't get you better speed, this might be a stable setup I can suggest:
ISP>Modem>Wireless Router(192.168.1.1, channel 3)>(network cable)>Powerline Adapter>Powerline Adapter>(network cable)>Wireless Access Point(192.168.1.2, channel 8)
In this situation you can count on wires to get your data where it needs to be. Wireless is always going to have hot spots and dead spots - that's the tradeoff for convenience. My experience tells me that if you have multiple wireless access points that are connected to each other by wired technology it is faster than if they were connected by wireless range extenders. All your access points should have the same SSID, same security settings, etc. but have a different IP address and use a different wireless channel. I've had the best success with hand-offs between identical devices in a configuration like this.
You can probably google some more indepth instructions on extending a wireless network, but anything other than the wired/wireless combination I describe above has always been less than ideal so I wanted to steer you towards what I know works.
Actually, as I wrote this I searched for powerline adapter/wireless access point combos, and it turns out there are some on the market since I last checked:
I'm not certain if you have the option of configuring the device to use the ideal wifi settings described above or not, but if you can it would save you some configuration... something I'll definitely be looking into!