I can certainly appreciate that. But I wonder about one thing. What about people who have home theater systems where the digital sound is played through quality receivers/amps and then to quality speakers? Wouldn't you want to have audio that sounded good through such a system?

Well when you consider the quality of studio monitors and good amps then your right there.

Even the cheepest JBL studio monitors play things I don't hear my computer speakers play. You got to assume they are as close to a high quality home theater system vs anything else.

I'm feeling the pinch so I think i'll buy a monitor amp today then build some speakers over the weekend. Any suggestions for a lower cost quality amp?

Overall, this is exactly true. On the video side, you can color correct through a junky Walmart monitor, or you can correct with a calibrated BVM monitor. At the end of the day, you can always suggest that "most people have the Walmart TV's" and that's probably somewhat accurate.
Or, you can realize that (if this is what you do for a living) that you need to not only meet the grade of the end user, but surpass it by at least a median margin, because while the Walmart TV owner might not miss it, the smaller percentage of very high quality gear will definitely miss the better video effort. Same is said for audio. For noise reduction, I use headphones in editing. For most everything else, I monitor on my Hothouses, Genelecs, or Mackie 626 system, depending on which room I'm in. For me, it doesn't matter if I'm doing a 30 second spot or a 4 hour doc for PBS, it effectively needs the same attention, and I need to hear everything with no assumptions on what the viewer/listener will be listening through. They might own a mono TV, a Bose home theatre system, or a high end set of Martin-Logan imaging transducers with a custom-built tube amp. My job isn't to worry about them, my job is to first satisfy the demands of the client, second to satisfy industry standards (as long as the client is in line with standards) and finally to satisfy myself that I've not let anything slip because I've invested in a good set of audio monitors that meet or exceed my ability to hear what is in the mix, and provide me with the palette I need, to work with, not work in spite of or against.
Audio monitors are your window to the final product, just like a video monitor is, and no less detail should be attended to for audio than for video. Even moreso, audio is far and away more important than video in most every production situation.