About to be a Jetta owner :)

So hopefully tomorrow I'll be the proud owner of a 2002 Jetta 1.8T :). It's silver, 5 speed, Monsoon sound system, power sunroof, all kinds of goodies and what not. One question though with the Monsoon sound system, I noticed there was a black box mounted inside the trunk. Is this an amplifier that could possibly power a set of 2 Pioneer 10" subs?
Also, concerning the stock diverter valve, I'm very interested in the blow-off sound that so many people want out of their turbocharged cars. I've been told by a friend of mine who owns a 2003 GTI 1.8T that a normal blow-off valve will screw up the way the turbo works. He said that the sound of blow-off sound can be achieved by using a CAI and upgrade the diverter valve, and the sound will be louder if the CAI is directed towards the wheel well. I've also heard praises of a diverter/blow-off valve hybrid. I've also seen the steep prices of these as well, compared to the prices of upgraded diverters. Should I go with an upgraded diverter valve and CAI for the blow-off sound or spend the extra money and install the hybrid valve?

Get a FORGE diverter valve and a short ram intake and you will be happy. Dont get a nuspeed intake or any filter that goes right on the maf sensor because they cause lots of issues with the sensor and give check engine lights.