I bought my Phoebus as a Solo card, since the price for the control to the full Phoebus was about 50 + Euros in Romania, got lucky and found one second hand for about 8 euros. I only use it for the Mics inside it.
You`re not missing out anything if you don`t have that control box that for some reason Asus asks a lot of $$$.
i7-4790k + Corsair H80i | Asus Maximus VII Ranger | 16 GB Corsair Vengeance DDR3 1866 | Sapphire R9-290 OC Vapor-X 4GB | Asus Xonar Phoebus + Audio Technica M50 | 1xSSD Corsair 120 GB | 4x1 TB Seagate HDD | Corsair CX750M | Corsair Carbide 300R | Razer Taipan + Logitech G11 | Windows 10 64bit