Speeding up data transfer?

you may be limited by either the NAS or the powerline adapter. Those things tend to never get their full speed and global performance vary depending on installations. Direct cable is always the best, but I think that if you got powerline in first place this is not possible. You could either use a better powerline adapter or use wifi N or AC if possible.
look at real throughput for powerline adapters : http://www.smallnetbuilder.com/lanwan/p ... harts/view

NV+ is not the fastest NAS on the market either. You could connect it to your PC to see the max speed (just give the two devices fixed IP on the same range), that way you'd know what you can squeeze out of it.
Jumbo frames could work, but your router/switch has to support it too, and given your computer I expect you to do something else than browsing the web, jumbo frames may increase the ping in games for example.