[mythtv-users] Powered 5.1 speakers or A/V Receiver?

[Norm]

I use Myth for basically my entire home entertainment setup.  I
currently use some Logitech powered speakers directly connected to my
Diamond Extreme 7.1 sound card.

Is this the best way to provide quality sound or should I look at
getting an A/V receiver connected via digital coax or spdif?

The current set up is ok, but I am looking to add perhaps THX support or
better/louder sound.

Thanks for any input --

Norm