connecting a sub to the left and right speakers

[pants1982]

I bought a denon htib a few years ago and it sounds find 4 inch satellite speakers and a 8 inch sub. I just bought the new denon 590 which has hdmi inputs where my old denon did not. My sub sounds fine on average scenes but when there is lots of action it can get overwhelmed quick, so I am looking into getting a new sub.

So my question is, if i hook up the left and right speakers to my old sub and use the new sub for the lfe channel. Can you tell a noticeable difference to the left and rights or would it be better to use two subs on the lfe channel?