FYI: just on the basis of indicated list prices :
Hepco-Becker 42 liter Journey side cases and SW/Motech quick-lock racks would cost around $795.
A top case and SW/Motech top rack would add about $300 more.
Going all GIVI (have to use a top rack to fit the side case racks and the 41 liter side cases) would cost slightly less (maybe 20 dollars less). Because the top rack is already fitted, adding a top case would add about $200 more.
It winds up being a matter of what look and features you like better and what deals below these list prices you can find. Start dialing.