Best XM from marantz st7100 or Polk xrt12

I run a Marantz SR7500 A/V unit with a Marantz DV7600 universal player and B&W speakers. What I want is to be able to add XM that will produce fairly high quality sound. I'm looking at the Marantz ST7100 XM ready tuner and the Polk XRT12. Does anyone have a suggestion or is there another similarly priced option that I should consider. Also, I'm hoping that either unit will sound noticably better than using my sky-fi 2 XM portable from the car. I tried it and it's not too hot. If it sounds just like that I'm not going to bother. Thanks,

You will need a separate DAC for the best sound but it will fall well short of CD quality. There is simply too much compression.
I have XM and love it in my truck, but I don't think it's for the audiophile system. Like Narrod pointed out, way too much compression.
I have the Polk unit and agree that a D/A will improve it's sound but not all that much. I use mine more for finding new artist and back ground tunes. The line up is great something for everyone.
I use the Polk xrt12 through an outboard DAC with superb sound. I listen to the classical stations (110,112, 113)and I don't hear the compression on these stations that people complain about. However, I do hear the compression on other XM stations. Also, I recently added Sirius through the same DAC. The classical stations on Sirius sound horrible. So, I wonder if XM uses different levels of compression on different stations. And I wonder if Sirius uses even more compression altogether. Does anyone know?