Interesting responses-thanks! I guess I have a bout of "upgrade-itis" and want to try something better, just to see what happens. I purchased some Signal Silver Resolution cables/IC's and it really brought the differences out between my Sixpacs and the DNA-125 (old cables were the Signal Analog 2's, which are nice and smooth, but not as detailed). Still, it is not night and day between these amps, and my wife said they both sound the same. I also had a chance to plug in an HCA-2 from PS Audio, and it was a bit more forward and didn't seem to go as low or sound as liquid, but was still good in it's own right.
I heard a KW500 at the dealer recently, and even though it is a big, powerful unit that retails at $7K (and was running off of a $1500 PC), I wasn't blown away by its sound on an Arial Acoustics 6 (which is a $3600 speaker). It had some of the same attributes as my system, but I wouldn't trade it for what I have. After hearing nice speakers run though cheaper amplification and mid-priced speakers run through high-end amplification the last few weeks, I am inclined to agree with those who think the speaker is where to start, assuming the source is accurate, and assuming one doesn't have an inefficient speaker in a very large room playing at high volumes.
Thanks for the responses. I have learned alot.