Mark,
The $1325.00 at Roeders was the 06 radio ($840.00 by itself), the XM unit and the big overlay harness. That harness, however, lets you connect up any other of the Advanced Audio accessories later on should the urge strike. So it's cost is not dedicated to just the XM unit.
Overall cost at $1325.00 did not include the rear amp. Total outlay for the radio upgrade wasn't $1325.00 though. I sold the 05 radio kit (radio,speakers, and that overlay harness you no longer use so the kit was complete) for $810.00 and a spare set of HogTunes I'd collected for $90.00. So only ended up with about $425.00 in the radio upgrade. That much lower total outlay made the extra expense for the great new amp kit from Hawg Wired much more palatable. The new radio, XM kit, overlay harness and amp kit are actually only in to me for about $1050.00.
I looked at the rear amp. Mounting and electronic audio specs are available. We could mount it (physically) without a problem. If you've got a fixed tour pak it wouldn't even be a bad solution. It's actually not a "great" amp as it delivers a fair amount of distortion well before it's total output is reached. But it'd be decent. Nothing compared to the clean large output of the HawgWired setup though; not even close. And not nearly so esthetically effective or pleasing as well.
With a detachable tour pak, however, the rear amp is very problematic. It has a huge harness and a LARGE plug that connects to the amp. Would be a real chore to cut that harness and a add disconnect for detachable purposes. Even doing so would still leave a big honking harness and plug exposed behind the seat. Just wasn't a clean way to make it work as a detachable unit. So went looking for something else.
That was about the same time Jim pointed me in the direction of the HawgWired amp kit. It's a nearly ideal solution. Small, digital (so no heat and low power consumption) and powerful. In conjunction with the 06 radio it is a great 1-2 punch. I wrote that it's a "nearly" ideal solution for two reasons.
It is a big pricey, for one. That's mitigated, however, by the facts that it works great and actually fits where we need it to. Nothing else seems to. Second issue would be for guys with rear speakers. It is a two channel amp. So a lot of guys will look at it and think you can't drive four speakers with it. The thing is that, in fact, you can. Just have to wire things up correctly. If done correctly there's no harm anyplace. The only "loss" would be the ability to control front to rear fade.