Lush,
If I worked for George Lucas, I would probably have a better stereo...
In fact, I used 2.1 sound in my HT system - I am more into audio right now.
I simply suggest THX as a simple way to assure you are getting a used mass marketed AVR that has the best chance to drive demanding speakers. These are typically the top of the line for any mass marketer and have the best preamps and power supplies in THEIR line. In the ultimate hifi sense of quality and performance, I would agree, THX is not "best".
Straight from the horses mouth below. Believe what you choose.
From THX website:
"THX CERTIFIED AV RECEIVERS
THX Certified Receivers are the centerpiece for great home audio systems. THX certification ensures that receivers can truly unlock the power of surround sound and deliver crystal clear movie, music and game experiences to your home theater or media room. By definition, a receiver is the combination of a pre-amplifier and a power amplifier.
Pre-Amplifier:
A THX Certified Pre-Amplifier not only goes through rigorous performance tests, but also embeds THX patented technology features. Through various combinations, these features are used in THX Listening Modes to give you the best possible playback experience - correcting acoustic errors that occur in the translation of content from the movie studio to your home.
Power Amplifier:
A THX Certified Power Amplifier is put through a series of performance tests that addresses items such as low noise, distortion, crosstalk, high output current and voltage. In addition, THX has interoperability requirements such as gain structure, sensitivity, loading and output. A THX Certified Power Amplifier works with any pre-amplifier and speaker system however, when used with other THX Certified components, you are assured of seamless compatibility."