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

If you want to make an educated decision, buy a dac based on sound and not specs.  For your purposes upsampling is when the sample rates are multiplied in hopes of improving the sound.  There are excellent products that use these techniques and others that believe that the less manipulation of the signal done, the better.  IMO, forget about  it.  

I have to concede that trusting your ears is not enough.  Unless you have ears you can trust.  

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.  

I think we're getting a bit off topic here.  I agree with what most of you are saying in principle.  I don't think there is anyone who would disagree that the best way to audition any component is in your home system.  But that's not always possible.  When I was purchasing my system, I would bring my CD player to the dealer in order to have some point of reference as to the qualities of the new player compared to what I had.  Speakers are somewhat different in that you never know how they will work in your room, which is why I had a home audition before investing in expensive (for me) speakers.  So I think we all pretty much agree on this.  But what I am saying, and I'm sticking to it, at least for now, is that knowing about the mechanics of upsampling or what DAC chip is not going to matter one iota to whether you will like the player.  I know some people believe that each DAC chip has a sound, or that a ribbon tweeter is automatically brighter than a silk dome and so on.  In my experience, I have found those generalizations not to be true.  But that's me.  

I've heard very good things about that company.  The home audition is very prudent.  Leave it on for at least 24 hours before doing any serious listening.