gm aftermarket stereo and alarm?

Hi all, Used to be a frequent poster, but then I got married and had a couple kids. It's good to be back. Anyways, my questions are these: I currently have an alarm system (installed by others) in a 2004 Pontiac Grand Prix w/ Monsoon. If I were to install a head unit WITHOUT the GMOS-04 adapter which retains the Class 2 Data Bus interface, would my alarm system still work? My intent would be to replace the stock speakers and power them with a 4 channel amp, therefore eliminating the need for the h/u to interface with the Monsoon amp altogether. My question is, which other features also vanish? Driver info, remote locks, etc? The chime and the steering wheel controls are gone for sure, but I just don't know about the ancillary stuff. If it were decided that I did need the GMOS-04, would there be any way to install this harness AND install (2) amplifiers? My limited experience with these harnesses tells me that the harness takes up (2) pre-amps, which would make hooking up more than one amp more-or-less undoable. Is there a way around this? A different harness, perhaps?    Thanks for reading, and please let me know your thoughts on my questions. Nate

Thanks for the feedback. I like that idea. So the Metra harness you suggest would plug into the 24-pin harness, and would provide connections for two wires (+12 Volt and Ground). The switched power source would come from a ignition-switched circuit in the fuse panel. I would lose my chime, which I can live with. Anyone see any negatives with this plan? My h/u is a Pioneer 6800MP. I am not sure if it will support a PAC SWI-PS or not, as those seem to be specifically for models with wired remotes unless I'm missing something. My unit does not have a wired remote, but it may have an input for one. Does anyone know if my h/u will support this interface module? Thanks again. Nate

And if I would only learn to Google shi+ before I post it, I wouldn't have to ask! Google tells me my h/u would support the PAC SWI-PS. So that issue is solved. But I would still like to get opinions on the harness plan outlined above. I don't see any flaws on the power side of things, but I just want to make sure this won't make GM grumpy.

when you have the factory radio in you can do some stuff thru the radio like program if the horn honks when you lock with the factory fob, how long your lights stay on when you get out of the car, etc. not saying it is a bad idea to wait for some others to give you input, but in the past 15 years i've done this type of install countless number of times without any repercussions. i'd say go for it. it should be an easy install for you since you have some background with audio

Yeah, I really don't see any negatives with the plan at all. Power is power and ground is ground, no matter how expensive the harness is. I especially like the idea of running wires from the Monsoon to the new amp. That will save me a lot of routing time. But who knows, I might run new wire anyways. Thanks for your help blanx. A lot of good info.