Just get an aftermarket one. Even the cheap ones are better then the stock ones interms of power output. Don't worry about the acoustic feedback thingy. I put a pioneer on mine and you can really tell the difference in the power from the head-unit. Preludes have pretty decent 6x9 in the rears that can take the bass, so don't worry about the whole acoustic feedback thing.
If you got some flow, get some decent componets in the front. Boston Acoustic or MB's should help. Would sound a lot better if you got an amp for it, but..... The stock speakers are pretty decent.

But yea, get an after market system. WAY better. looks cooler. only thing.... attracks the attention of thieves. Good luck.

Oh, I do installations and did both mine and my brother's prelude. Very easy to install.