Use Devolo/TPLink Powerline. I get near maximum speed through the TPLink 2000mbps setup.
For wi-fi, I gave up on SH2 and put it into modem mode, using my trusty Asus RT66 the connection and wifi has been rock solid for nearly a year now.
Could you link to the exact TPLink you use please? I'm desperate to get some Powerline networking in my house but put off by reviews saying they don't get anywhere near the speeds advertised.