The THX certification doesn't denote any special signal processing. All it means is that the receiver meets certain audio parameters, nothing more. Personally, I wouldn't go too nuts with a DVD player just yet, as we're at a point where technology will be changing soon. Get a plain-jane "el-cheapo" from one of the predominant manufacturers (i.e. panasonic, toshiba, pioneer, etc.) and you will be very happy, as you will get your 5.1/7.1/whatever from any of those units.