I noticed to get my sound right
I'm recording with a stand-alone portable recorder
What are you recording? We never established what the show was. The DR5 (they insist it's a DR-05) is a perfectly good live recorder and has provision to plug in modest computer microphones and the instructions claim that if you're really, really careful, you can plug in an external stereo connection.
My impression of the little connection between the two microphones is a Try To Do Everything socket that seems to be gaining in popularity.
Once you record/digitize the show, the quality will stay constant as you move the sound files between machines and locations on the same machine. This is where digital audio is a really big deal. It's hard to break, but you can see the storm clouds gathering. Open the show in Audacity, do some really tiny harmless edits or cuts and export a new show. Because of the way Audacity handles the work internally, a tiny dither (noise) signal is added. So technically, this is the first time the show quality is very slightly less than it was when you started.
The obvious shortcoming we have been talking about above is how do you listen to the show while you're editing. How can you tell what you have? The argument immediately splits into two parties, and you've already run into this: Listen to the show on a perfect monitor system, or listen to it on the devices the client is going to be using. There is no right answer. Many people mix, filter, effect and post produce on perfect speakers and check it on an MP3 player
just before they deliver to the client.
an "MP3 Player Show" can be dangerous. Suppose the client gets a new player? Suppose, as recently happened, Apple starts issuing really sucky earbuds with their iPods that replaced the better, old style. Now what do you do?
If you have several music systems that you expect to all sound the same and they don't, there are tests you can do. That's the pink noise thing. Pink noise is that rain-in-the-trees hiss that contains all audio tones spread out in a precise way over time. If one of your players has trouble with some music tones, this is the test to tell you. But it's not a beginner test. You don't have a beginner problem.