If you have a good whole house wireless network, you could use a TPMC-3x for handhelds, with an iPad for the main zone. You would use an IP capable control processor with this system.

If you are satisfied with the basic Crestron Mobile Pro G GUI for the iPad (no support for swiping and gestures), you could use an Adagio AADS-XM which has a built in XM tuner. This would serve as control processor and audio distribution unit.

Not quite sure why you would need Sirius rather than XM, but if Sirius is required you could upgrade the AADS to an AES-SRD which has a Sirius tuner card. Or you could go with an AMS-AIP-SRD which has control, whole house audio distribution, Sirius tuner, and home theater receiver all built in.

If you want the fancy Crestron Mobile Pro G iPad GUI, you'd need a control processor with compact flash such as the PRO2.

I generally will do the TPMC-3X over wifi when I am specifying and installing the wireless network myself, and thus can guarantee that there is good coverage throughout the entire home. Using a commercial grade WAP such as Pakedge is key.