OK to use Splitter for 2 Subs-Receiver has 1 port

I'll second what Kal said.

Dave

I'd not be inclined to used 2 different subs - basically the sound mismatch. As for the onkyo, you could use the sub out for one, and a pre-out for the other. Of course it would make setting up a mess.

I'm surprised Onkyo had an issue, you are just outputting a raw signal. Lots of people use 2 subs. But, heh, it's their product, they should know best.

Yes. However, you should (1) place them equidistant from the listening position and (2) adjust them for equal output before you do your full setup because you have only 1 setting for subwoofer distance/level in your 905. Stacking them might be effective.

Kal

Onkyo might know a tad bit more about their products than folks on an audio forum. Just a thought.