I find THX rolls off the top end somewhat. This can be useful for later night listening or if the sound-track is very tiresome (e.g. lots of gun-shots and breaking glass). Generally though for discrete (5.1) codecs: DTS and DD, I listen using Cinema. PLII and PLIIx (7.1 system now gone) are nice for DD2.0 and PCM film sources. To my ears THX Ultra is unlistenable for more than about five minutes, making me feel nervous and uncomfortable and just sounding horrible.

There is no "should"; its your kit and your ears.

In the spirit of Spinaltap, I would like to confirm that I am not involved in the corrupt theft of a global sport.