yes, just split the signal. It won't hurt the sound unless you split it like 15 times.
The 7.1 is 7 speakers, 1 subwoofer. You should not run a subwoofer from a speaker output, unless its a main speaker and your running the subwoofer on the highlevel inputs.
Nevertheless, don't hook your sub up using the speaker level outputs if you have RCA line level ones.
Get a Y-splittyer with 1 male to 2 females and your set.
SheepStar