Good luck finding music recorded in 5.1. That format died years ago.
I beg to differ. There's still quite a bit of stuff being recorded and mixed in 5.1 audio. They are just in download format and not physical media anymore. I'll have to dig out the websites that I know are selling them.
Regardless, durkmusic admitted that he doesn't know much about this stuff and I think he is like anyone else who doesn't know anything about car audio in that he knows what he would like to have but he doesn't necessarily know the reality of what he's expecting to get. Bottom line is you can do anything you want to your car. It's yours. If you want to put five cheap speakers in your car and you end up liking what it sounds like, then great. What sounds good and what showing off to your buddies means is subjective. So go for it if that's what you want. Part of the fun of being a car audio enthusiast is the ability to try things out and then try something else out to see if it works better or worse than what you've already tried. If you don't consider yourself a car audio enthusiast and you just want something that "sounds better" than stock and, in your case, 5.1, then basicly anything you do will sound better than the stock system.
If you really do care about the overall quality of the music you will be listening to then I would think you'd want to keep your mind open to whatever true audio enthusiasts would say about your situation and I feel that has been represented fairly well here on your thread. But, again, it comes down to what you want and like.
I am of the opinion that 5.1 doesn't work all that well for cars for the same reasons already given but that doesn't mean you won't think it's the best thing since sliced bread in your car. I will also agree with others here that $400 is going to be a little difficult of a budget to get something decent. Can you get something that sounds better than your stock system for $400? Yes. Is it going to impress your buddies? Maybe. There's all kinds of levels of equipment to meet whatever level of budget and/or opinion of "quality" you have.
Good luck and keep us posted as to what you do. I can't speak for everyone on this forum but another part of being a car audio enthusiast is finding enjoyment in seeing what others have done. Sometimes it sparks more ideas. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif