What can i get?

[KenC]

There is no reason to throw down the extra $200 for that Nak CD-400. Unless you shell out $200+ on interconnects and speaker cable, as well as $500+ on a set of components you won't be able to tell the difference between the CD-400 and the Clarion. The Clarion can also change colors to match the lighting of the e30 (over 80 different colors). I suggested it to him because it's inexpensive, it has 3 sets of preamp outs, it has a decent 1-bit D/A converter, and the illumination will match the interior.

[KenC]

getting a 4 channel amp that puts out 40watts/4 is just stupid, particularly when the deck you want will be just about the same.

That clarion deck will put out no more than about 18-20 watts RMS. They always list the 'peak' power to try and dupe you into thinking the deck has lots of power.

The a/d/s/ PQ10 was bench-tested by Car Stereo Review and it put out 62 watts RMS x 4-channels at 4 ohms. 62 watts RMS (peak ~100) is plenty for a set of components. Most people, myself included, probably wouldn't be able to tell the difference between an amp with 60 watts rms and one that puts out 80 rms (the increase in loudness will be miniscule).
I also recommended the a/d/s/ PQ10 because it's still regarded as one of the best 40x4 amps ever manufactured. It's also readily available on eBay for ~$100 or so.

[KenC]

I've listened to the Diamond Audio Hex series extensively, and they sound great. The M5 series are the level below the Hex; the major difference between the two is the crossover, not to mention the different cone materials.
The Diamonds will be 1000x better than the shitty stock speakers as well.