Now that I have solved the problem with a bad rca cable causing bird chirps in my rear channels I am running the gain on the OEM-1 at max.
I have an Alpine 4 channel amp (MRV-345 @75wpcx4) running 4 Infinity 6.5" door speakers with the Infinity tweeters in the stock dash locations at the moment as I'm still trying to come up with a sub solution that doesn't involve a box in the luggage area.
I can adjust the gain on the Alpine amp but it is running at factory default right now (about half way on the adjustment pots) and with the OEM-1 running wide open I have no noise at all. I'm also running the stock "subwoofer" from the Bose amp and since the Bose is only running the sub it doesn't sound too bad actually. The Bose seems to have more control and maybe more power because the bass sounds tighter from that little rinky dinky 5.25" woofer.
I'm running the Alpine amp full range and if I ever get a sub figured out I have an Alpine MRP-M450 mono amp to drive it and I'll try switching the 4 channel amp to high pass and see how it sounds.
I listen to a lot of jazz and older rock and it sounds pretty good right now, a lot clearer and more detailed than the Bose system and there is actually quite a bit of bottom end and it doesn't sound so muddy as the stock system.