I've been putting a lot of thought into sounds in the 500E. In terms of headunits, Nak is a good call but the future of the company is in question. Knowing your price range would help my suggest a few units. If you plan on getting a CD/MP3 changer, I'd look at some of the newer alpines that have the fold out screen. The have a very minimalist look and a very laid back display.

In terms of bass, it all depends on what you like and what you listen to. For me, a sealed trunk that vibrates the cabin will never be acceptable. I can't stand the sound of muffled bass, no matter how hard it hits. If you want a subwoofer in the trunk, you must port the sound into the cabin some way and there aren't many options given the location of the gas tank.

I'm really leaning towards trying free air which is a dying setup but which can provide very good results if done right. I've heard that a single 12 or 10 in the rear deck where the first aid kit is will impress anyone but the biggest bass heads. Unfortunately, I can't comment first hand.

In terms of component speakers, I would get my head unit and full range amp and see what I liked and didn't like about the factory speakers. Sometimes a factory speaker will sound better than anything else you replace it with -- especially if it's an irregular size.

In terms of speaker placement, you said you weren't an audiophile. Well that's important because if you aren't hell bent on getting great imaging from your music, there is NO reason to cut the door panels.

In short, I believe you can get good clean sound with a new headunit, the factory speakers and an amplified subwoofer that either fires through or is ported through the rear deck. I've been putting high end car stereos in my vehicles for the past 15 years and I know you cas get good sound without spending lots of money. Great sound in a car, well that's another story.

Sorry for the long post. I'm kind of tired now. Must go sleep.