I run from pre outs on the HT receiver to an input on my stereo preamp and match levels (requires a microphone and set up program)
If your main speakers are of sufficient quality, consider going with a phantom centre channel.
This set up allows you to cross over higher than you would normally for your speakers (even if they have good low frequency extension) and redirect low bass to a dedicated subwoofer if you like.
Also, set up your stereo system to get good imaging and then leave them there for movie use. This may limit the size of screen you can use. If the spacing is closer together than you need for a screen, go to a sonically transparent screen and have the main spekers behind them (screen has to lower from ceiling)