On your remote there is a button that say's "Pure Direct". This sends everything to your front speakers bypassing all the other circuitry, including subs or any other speakers you have. This is strictly for 2 channel. In essence, your receiver becomes an integrated 2 channel amp.

If this still doesn't do it for you, I might suggest a sub running off of your Left and Right Front Pre outs. (This is for "Pure Direct" mode only) Do not use the Sub Pre Outs in this configuration. If you do, switching to "Pure Direct" will cut the sub out of the circuit.

Your other option with a sub, is to connect the Sub to the Sub Pre Outs and select the "Straight" button on your remote. This mode allows access to speaker configuration and tone controls, which you may have to adjust. The advantage of this configuration is that it works equally well for surround when you get your other speakers.

I hope this helps.