I have an 04 Tacoma and I am interested in installing xm, and I am looking for some input on the best syestem to buy and where is should mount it.
Here is my only stipulation, I want to keep the stock headunit for so don't tell me to buy an xm ready headunit.

 

Look at the XM Commander for a permanent mount with remote or the Roady2 if you want to move it to another vehicle. I've got the COmmander in my wife's (my former) 4Runner and it works great, nice big two line display. As for wiring, you'll have to have it installed with the FM modulator since the OEM headunit won't accept direct connection. THe other alternative is to get the Scion/Pioneer headunit off eBay and the XM kit from Toyota for a true stock install, except for the green lighting of the Scion HU.

 

Is there a reason you picked xm over Sirius? Just wondering.
I just finished an install of a "Plug and Play" unit, which I think is what you want. I thought I wouldnt like the big portable unit, but the display on it is key.
I love all the extra features I get w/this unit, compared to a headunit w/built in controls and only a 2 line display. I can browse all the other channels to see what's on, and I can mark any song(up to 20), so that the next time it is on any channel it will alert me. Here's a pic-

 

Oh yeah, not sure on the XM models, but with the Sirius PNP's you can get an adaptor to "hardwire" it to your stock unit. The fm modulator isnt the best way to experience the sat. radio. Especially if you live/work where there is crappy reception, or tall buildings

 

The reason I picked xm over sirius is because I had a friend who has had both systems in the past, and he recommends xm. The main thing he said that made me want xm was that sirius lost signal much more easily than xm.

 

That's cool, I havent run into that yet, just lose it under bridges/overpasses, etc. I have heard that XM has more terrestrial repeaters to keep the signal strong in all areas.
Maybe take a look at the different stations they offer too, if one provider has better content or not.
Sirius was an easy choice for me: NFL/NHL/NBA, Stern coming in '06 and the online streaming ability so I can listen at work without using the unit.

Good luck w/install, post some pics when you get done!

 

The adapters are't brand specific, they're "just" creating line-level AUX inputs in place of external CD or changer connections on the radios.

PIE and Blitzsafe are the two companies making adapter cables. There's info here.

For deals and such, it's worth a visit to XMFanStore.com and MyRadioStore.com.

 

Here are some pics of the install:

 

I have a new XM MyFi on its way and will have to figfure a way to mount it in my 99 4Runner.