Sync'ing over Wifi is SO SLOW

[TechDave88]

I just bought an iphone6 (ios 8.4) w/ latest Spotify version. 

I'm using desktop Spotify 0.9.15.27. (b/c it has the devices tab)

I am trying to sync my offline/local files but it's so very slow  I did the no-autolock and left Spotify sync'ing over night (~6hrs) and it sync'd just over 40 files. 

I'm trying to sync about 800 spotify files + my offline/local files.

The whole point of upgrading my phone to something with more memory was so that I could put more of my music (local files) onto my phone to listen to via Spotify. 

I've been digging through the community and this seems to be a long standing problem..

Is there another way to transfer files other than via wifi? 

Can I load my files to my iphone via itunes and have Spotify use those for offline sync?

Any help would be greatly appreciated.

-Dave