from what i have read, you will need the toyota interface box to get the oem head unit to run the xm. Being a xm install veteran, the xm units connections are universal, as to facilitate hook up to any antenna and HU. So any brand of xm receiver will work with any xm ready HU on the market. Its all a matter of having the correct interface cables.
Now it you plan to keep the car longer than lets say 3 years, IMO, go the stock install route, but do it yourself to save the install fee. the directions to do it are easy to find and to follow.
If you are like me who trades cars like sex partners, then go with a Roady or a portable type xm unit that uses the RF input for the xm, sure you will have to hide some wires and may not have cosmic sound quality like a hard wired unit, but only your dog will really know the difference. And when you trade up for a new ride you will have xm johnny on the spot ready to go in your new ride. The Roady is practically free if you go through
COMPANY SERVICES | XM.COM to buy it, with rebates and all that or shop on ebay and compare.
I hope this helps
hjb