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,

Mike
ndfan
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.