My goal for the audio system was to have something rivaling a premium new car. Balanced, lots of low end, but not overly bass heavy with a clear and detailed high end. All in a somewhat stealth install without doing a whole lot of hacking up the car. Also I didnt want to break the bank on this either. A high end amp can go for $1500 alone and thats more than my entire install so selecting components would be crucial to getting great sounding pieces at great prices. If budget wasnt an issue, I could rattle off some pretty high end coomponents and it would add up to about $5k, and sound phenomenal. I wanted to get the $5k sound on a MUCH smaller budget. I started with the head unit. This is a key component, if this sounds bad, then the rest of the system will sound bad. I want it to look clean, maybe a bit plain. Something people wouldnt look twice at. I decided on teh Nakamichi CD500. These have not been made in a while, but you can still find them new at a few places and they are known for the sound quality. They have a built in 3 band EQ, subwoofer control and output, 4 channel line out in addition to the subwoofer out, digital input, plus analaog input (crucial for the iphone connection) and a nice clean, no nonsense looking unit. The speakers were not as hard as I thought. Went to a few places and decided on the Hertz HSK 6.5 2 way components. The company is a sister company of Audison which makes AMAZING amps. The hertz brand has been known for giving you the Audison Italian made quality at about half the price. These speakers have been rated as the best component speakers year after year. You would have to spend about double to get any better. The amp I went with was a Soundstream TN5.950. Its a Class D digital amp thats very flexible in its configurations. 5 channel, 4 channel, 3 channel whatever. Has a dedicated subwoofer channel and has crossovers on all channels. Puts out 80 watts x 4 plus 270 x 1. Or it can be bridged for 250×2 and 430×1. Its also using the same board design and chipset as the Polk Audio, Hertz, Precision Power and NVX amps. Its about 1/3 the price of the Hertz and 1/2 the price of the Polk Audio so I was hoping to get sound quality approaching or equaling those amps. The last part was the difficult part. The subwoofer. I found a guy who builds custom boxes to fix under the rear seat of the BMW 2002. The problem is he designed it for a 6.5″ subwoofer. It has .15 cubic feet of space inside which is tiny. I wasnt sold that I would be happy with the output of the 6.5″ sub and I wanted to go with an 8″ subwoofer. The problem is that almost every 8″ subwoofer was either too deep and/or required at least .3 cubit feet of space. I couldnt double the box size or make it deeper. There are shallow mound subs designed to fit in tight places, but those usually sound awful because of the design limitations. Then I found the Alpine Type R 8″ sub. Designed to work in .15 cubic feet of space and it was only 4.5″ deep. In addition to that the magnet did not vent through the rear like some subs so the rear could be flush with the box. So I ordered the sib box and the Alpine sub from 2 different places and crossed my fingers. The Alpine sub is a monster, will take 350 watts RMS and a peak of 1000 watts! That means my 270 will work perfectly. How will it sound in such a small box? I couldnt find any reviews of it in a tight space. All reviews were inlarger boxes but they were ALL very positive about how clean, and clear they were as well as getting deep frequencies. The sub box arrived and I looked it over, very well made, came with Polyfill already inside. I marked out where I was going to cut to make the 8 fit. Grabbed the dremel tool and a few minutes later it was done.grinded the hole down to smooth it out and test fitted the sub…perfect! I put some weather stripping around the mounting hole so the sub would be airtight. Marked the mounting holes, grabbed the drill and the sub was ready to be screwed in. What a breeze! Wired it to the amp and turned up the gain….WOW. Tight, clear and deep bass. No rattles, no creaks, just clean sound. Adjusted the crossover a bit and the subsonic filter and I played a variety of tunes. From Beyonce to Black Eyed Peas, to Muse to Depeche Mode to Steely Dan to Stevie Wonder. All sounding great! From the head unit I have the sub at about 5 or 6 out of 10. Its that loud that I have to turn it down. I also did not set the gain very aggressively so there is probably room there as well. In conclusion I have a VERY good audio system at a very good price. I did all the wiring and installation and that saved alot of work. Its not that difficult, just takes some patience and dedication to do it properly.