i have this issue too... not only with 4790k and 4770k even with 2600k... http://hwbot.org/submission/2594424_
if you click on XTU setting in the result page it shows 49X multi.. but in screenshot the Xtu's window shows 5ghz which is not true...
Xtu is all about Memory, so you need better mems not higher cpu clock for now , 1018 was my 4100mhz test... 1116 will be a good score on 4500mhz and for 4600mhz --> 1130+
actually i benched it for wprime32 and 1024 before (5860 wprime ) but cinebenchs and Xtu still are on the table , after your 2600k xtu it's my turn to get 2500k xtu cup lol