What is the difference between Sirius Ready and Compatible? Any receiver already come w/built-in tuners?

Looking to install Sirius soon in my xB. I have a JVC Sirius Compatible, but haven't got a tuner yet. I'm thinking of swapping out my JVC LH300 receiver for a new receiver/radio because the reception currently stinks for AM/FM. Though I'd ask about the ready/compatible issue before I purchased a new receiver. Thanks.