Would someone explain what "up sampling" means and how it can affect the sound?

Well, I agree with chayro’s statement and disagree with gdhal's statements, "Seems to me it would be best to make an educated decision based on all possible information available. That would include specifications, your own subjective listening, opinions of reviewers, value of the component, etc." You don't listen to specifications and just because a reviewer raves over a unit doesn't mean you will like it. Bottom line is you buy what your ears like. Too many people buy for the wrong reason, and all you need to do is trust your ears.

I cannot tell you how many posts I've seen in which the person is looking for a DAC with a certain chip or a speaker with a first-order crossover, or a diamond tweeter or whatever.  IMO, it all doesn't mean a damn thing. It's how the product works as a whole that counts.  But then again, I truly believe that many audiophiles have no idea of what they're listening to anyway and just make purchase decisions based on reviews or pictures or whatever.  Of course, it's their money and their choices, so everyone is entitled to enjoy this hobby in their own way.  I just think that many audiophiles would be happier with their systems if they just listened more and read less.  

Oversampling - integer multiple of original rate
Upsampling - non-integer multiple of original rate

For instance, my Benchmark DAC1 is upsampling (and not the oversampling) DAC,

Specifications relating to how devices interface with other devices are always important. Many examples some of more consequence than others, but you ALWAYS want to know if or how well one device will work with another before buying.

Other specs or aspects of design are of interest also of course but harder to "bank on" in that there are so many factors that go into a quality design and product and what people judge as "good sound" that you never really know for sure what's good for you until you hear for yourself

tls49 and chayro - ordinarily I would ignore such a foolish and technically inaccurate response (from the both of you), however, I have ample time and desire to stir things up a bit to reiterate how wrong you are. Nowhere have I stated that someone should not listen with their own ears. What I have stated is that doing so is simply one more variable - albeit an important one - to the overall decision making process. The both of you, on the other hand, have gone as far as to completely discount everything except listening. And that is ridiculous, among many other other adjectives.