I'm hoping to get my Alpine head unit and empeg installed in the dash this weekend. Is it possible to power both head units from the factory wire harness? I guess only switched power, memory, ground, and dimmer would be shared. Is that ok?

Should be just fine. Try to make the power and ground wire runs to the factory harness as short as possible and be the same gauge wire. For both the Alpine and the empeg. That will reduce the chance of a ground loop between the two devices.

I tried that for a while in my last car (Mitsubishi Galant) and I would occasionally see my empeg bounce into standby, and then back on. Running the memory power wire directly to the battery solved it (fusing it of course!) I'd say try it, and if you see it drop into standby mode, run to the battery directly. I still kept the switched & ground into the harness with no problems.

Thanks guys! Looks like I will try the easy way first.

Well, I did get my install done that weekend and it works great with both the Alpine HU and empeg running off the car's wiring harness.

One issue with this particular car (1998 Isuzu Trooper) is that it has two antenna connections. One is standard and the other looks like a GM-type. It doesn't seem like one is a power lead, but the radio reception is crap with only one or the other connected. This isn't really bothering me since I have XM on the Alpine and that kicks the crap out of NY terrestrial radio. I guess I should ask Crutchfield about this, but this truck isn't exacly a normal model for the year. Instead of the standard antenna next to the hood, it has two glass antennas on the rear side windows. I would assume they're powered, but I don't see a lead for that.

Anyway, pics are coming, but it's always too dark out when I have time now.