wiring headunit sub out to stereo amp.

Hy.I have a stereo amplifier wich is conected to a subwoofer in bridge mode.I recently got a head unit Blaupunkt Mp56 wich has 2pairs of preout for amplifier,and an 1rca preout for subwoofer.How can i wire that 1rca to amplifier's 2 inputs(L+R)-i want to use it for access the subwoofer gain control in headunit.If i wire the sub-out preout only to one amplifier input (L or R)the power will be half?Or if i use a RCAsplitter to make that one sub-out divide in 2  to connect to L and R inputs on amplifier the sound could sound weird because the same mono signal would enter in Left input and same in Right input of amplifier?Or should i just use the 2pairs of preout,wich head unit also has for powering rearspeaker amp.,but i would not be able to set levels for subwoofer from headunit menu.How should i do?

 Use y-adaptor it will be fine