what are the specs on the soundstream amp? At the moment I would keep the monsoon amp and add a mono amp for a sub till we figure out what to do about the 8 speaker setup.
To replace the monsoon amp, you need to find 4 passive crossovers (and the correct crossover frequencies). It shouldn't be too hard, I just haven't had the urge to sit down and figure it out yet. MCM Electronics has a wide selection of passive crossovers to help get you started. Their website is rather annoying, so you should request their full catalog to look at.
http://www.mcmelectronics.com They also sell other useful carputer -automotive stereo items and more.
Do you plan to install a carputer to replace the HU, or will you be using a an aftermarket headunit too? If you are installing a new headunit, I highly suggest you listen to the monsoon amp with a high-end aftermarket headunit first before you cut the cabling and remove it.
I originally was going to go your route, and changed my mind after hearing my new HU and the monsoon amp. It's very clear and loud!!
