Basic car XM install questions

Hardwire power is easy. Use the 12v and Ground from the radio. Get a long enough wire(s) just splice and connect hot and cold from the factory deck.

For the best audio, yes I'd use a cassette instead of a modulator. FM modulators have awful SQ from my experience.

As for parts, all you'll need is some wire from your local electronics shop to wire up the SkyFi2 to the deck for power.

What type of car is it? If it's not a lux car and doesn't have all those electronic gadgets, you may want to just install an XM tuner and a new CD player that's XM compatible. That's what I have in my Explorer and I was too happy to pull that factory crap out. I lost my steering wheel controls, but oh well.

Even if your car does not have an Aux in I would highly recommend you modify the harness to add an adapter. My Audi TT did not have an Aux in and I did cassette input for awhile and tried FM but the Hardwire is so Much better it is worth the extra trouble. Modified Harness's can be found for many cars. Mine used the external CD input as a means of adding the jack.
-Craig