I think how good something sounds depends on how it works with the limitations of the rest of the system. The UDP might sound great in one guy's system and be hardly distinguishable in another system. If you asked both guys what they thought of the UDP, you would get one rave review and one bad review.

If you know your system and its components really well, you are in a better position to determine what components are contributing which chacteristics to the sound. This would allow you to make a more accurate evaluation as to the subjective worth of a new component.

There are a number of universally impressive components that please a large percentage of audio geeks, but there are a lot more that sound good in some situations and not so good in others. There is even a smaller number of reviewers capable of describing the sound of a component to the degree necessary to justify purchasing without auditioning yourself.

This is taking the long way around the barn to say, there is no way I would spend serious money on a new component that I have not listened to in my system. Naturally, if you buy right and can recoup a good chunk of your investment if things don't work out, well, that's a little different.

I agree with the system matching concept. However, and even more granular way of stating the same is: "How transparent are my amplifier(s) and speakers? (and, perhaps, "preamp")

I have a setup that is truly transparent, IMHO. Therefore, the differences between source components are audible. If you own speakers or amplification that do not provide a good, flat response, then spending big bucks on sources to get the Nth degree will not bear fruit. And, comparing source components will be frustrating.

I can take my DAC (which is humble by the standards of many) and plug it into my buddies system, which is built of of good early 90s style components, and it does not sound much different than his Marantz CD63. The same DAC plugged into my stuff left my friend slack-jawed; then he went out and bought new stuff.

If you have good output components, the I say go for the good input components!