jusatry

i am replacing the HU on my 03 A4 with a computer which puts out 6 channel sound through three mini-jack outs. I have the Symphony II with bose. So what i am going to do is tap the lines for line out RF, LF, RR, anf LR from those corresponding RCAs from the computer. The sub line out is going to go to my aftermarket sub/amp.
So my question is this: do i need to wire the center channel in somehow, and if so how? i dont really care about true 5.1 surround sound but i am concerned that if i dont wire the center in somehow the signal level will not be high enough to get good sound output.

Any help much appreciated.