Well the reason is that Cannon open pit has been very very good...

Well the reason is that Cannon open pit has been very very good to the economics of WGX's SKO operation as the rent Bell Potter research note points out (available on the WGX website) . If as seems likely that Cannon UG is very possible and if open at depth, then it would very very economical for WGX as all the infrastructure established (and paid for) for the open pit is useable, and the deposit is open at depth so the mine life may last for a decade or 2 ? Then all the other SAU's other very exciting exploration assets come for free. SAU is debt free, and the Mkt Cap equals cash backing (most Cannon open pit receipts still to come), so an acquisition by WGX would almost self funding, especially when strip out 'overheads' .
In a world dominated by ETF's these mid tier's must strive to be NST look alike's or else have poor performing SP's. EVN saw the writing on the wall and used its elevated SP to diversify and expand its MC.
WGX plus DCN ..... wow or OGC + WGX or DCN double wow ... who knows.
I do hold SAU, so I have an interest, and am considering WGX and DCN which especially looks good value.

• Bell Potter Feb’17 research note excerpt "Although mining at the South Kalgoorlie Operation (SKO) continued normally through the quarter, the majority of the plant processing capacity was devoted to the Cannon Gold Project, in which WGX has a 50% profit share. Whilst some of WGX’s directly owned ores from HBJ and Georges Reward were processed, most of the directly owned ore was stockpiled during the quarter. Equity production (after including 50% share of Cannon) was 16.2koz, up 31%. It benefited from the big processing campaign for the Cannon mine. Even though that Cannon production was at an impressively low AISC of A$743/oz as mining of the highest grade ore at the base of the open pit occurs now as the pit nears the end of its planned life, the average equity AISC for SKO was only down 5% to A$1,305/oz because the average AISC of directly owned ores was up 13% to A$1,664/oz. Underground production from HBJ improved as ore development from the virgin SOZ lodes began to impact on overall ore grades and stopping output from the HBJ lodes was lifted by 42% in tonnes and by 8% in grade;
•  The Cannon mine, in which WGX has a financing and 50% profit sharing agreement (after repayment of all costs) with Southern Gold Ltd (ASX – SAU, not rated), performed very strongly as a significant part of its ore that had come from the highest grade part of the deposit at the bottom of the pit was processed. Total gold production from Cannon was 12.7koz at an AISC of A$743/oz. A larger stockpile of Cannon ore will be processed in the March 2017 quarter; "