Slightly OT, but I felt I should inject this into the discussion based on the last few posts...
There is no credible evidence to suggest that cost is directly related to any audible improvement for amplificiation ( as compared to what can be purchased at lower prices from non-exotic brands ) once you get into the 'high-end' sector.
As has been said many times before, speakers are by far the most important part of your hardware selection. DO NOT go to a lesser speaker to get a 'better' amplifier.
For the most part, the standard amplification stage of the typical name-brand receiver should provide transparent amplification in most situations. In those cases this is not true, it is either an *unusual loudspeaker load/demand, the user has unusual demands of the amplifier, or perhaps an audible noise/hiss problem, or likely even the listener's imagination ( which seems to be most often the case for many thing in audio!

).
*If one needs an add-on outboard amplifier that can drive virtually any complexity (inductive/capacitive reactivity of abnormal degree) of load because of an unusual loudspeaker load, that still is no excuse for relatively expensive amplifiers. You can find professional audio amplifiers (or in some cases, value oriented home audio brands such as Outlaw ) that will do the job perfectly, and be lower in cost compared to most comparable home audio amplifiers sold by popular brand names. One example is a Behringer A500. You won't phase it, even with loads at 4 ohms with +/- 60 degree electrical phase swings. 138 x 2 @ 8 ohms, 220 x 2 @ 4 ohms, and only about $200.00 shipped, there is no excuse to go to exotic amplifiers if the only purpose is to get a transparent/linear amplifier. Of course, if you want other things, such as specific aesthetics (
personally, I think the front plate on the Behringer mentioned above is hideous ) or name, that is another issue. But if you are on a tight budget and want just the performance, I can not see why one would spend more for what amounts to cosmetics/name, unless one had to in order to get a specific feature set/specification that was required for a specific situation.
-Chris