Well when you play your mix in someone else's stereo, listen to a professionaly recorded CD in that Stereo as well. This will give you good reference as to what a mix is supposed to sound like in that particular stereo. If you listen to the pro mix and you can't hear the kick, then it's the stereo's fault not yours. But if you can here the kick in the pro mix and not in your own, then you may have some work to do.

One suggestion I would have is to boost the kick somewhere between 2.5k-5K with a narrow bandwith. This helps give the kick that click sound, which always helps it cut through even in the crappiest speakers.

Another suggestion I would have is to mix without a subwoofer. Remember that most stereos out there don't have subwoofers so it would probably be best to mix without one, most of the time. I would still use it as a reference however.

The ultimate goal here is make a mix that sounds good in any set of speakers you put it in. This takes a little bit of experience. Before you finish your mix, make sure you test in as many different stereos as possible.

Before I give someone my final mix I make sure it sounds good in my monitors, my crappy 1 inch mono computer speaker, a crappy little stereo, a good stereo, and a big huge massive car stereo system. If it sounds good in all those, or sounds how it's "supposed" to sound then I know my mix is ready to go.

Hope this helps 8-)

I assume you're working in digital. Use a low frequency rolloff at around 30-50 Hz. If you don't ,you're adding a lot of garbage down to 5Hz that a standard system will struggle to reproduce and not be able to. It will only add a bunch of mud. Johnjm22's right. Lose the sub while mixing. Also be sure to define different fundamental frequencies for the kick and bass.