When I went to Sam Ash, I asked for something good and affordable. This is one of the sets they recommended. I mentioned they sound great for listening to vinyl, because if someone were looking for an affordable set of speakers for a system, these are definitely worth it.
The studio I used to record at had a pair of speakers about the same size as the 20/20, and a massive PA set in each corner. As we'd mix he'd switch back and forth from each to be sure everything sounded right. Of course Elvis once recorded on his 24 track console when it was in TN. Even though he had excellent equipment and he was a complete pro, he'd still send us home with a cassette each night to try out on every sound system we had.
Once you've used a certain set of speakers long enough, and have heard the mixes on other speakers, you get to know how you have to adjust to balance the sound.
In the end, if you know what you're doing (I know I don't), you can mix on a set of $25 computer speakers.
When something sounds good, it just sounds good. I don't change anything till it breaks.