I'll second Sams opinion on that. I too originally got the FM modulated kit as I didn't want to change radios then (also when XM radio first came out, over 1.5 yrs ago) and I had no complaints about that setup. Actually, it's nicer than my present setup in a way because with that kit, you can always see what's playing on XM radio even while playing cds or tapes if you have a tape player.
Last winter my old cd player/radio died so it was upgrade time and I then bought a nice XM ready Pioneer cd player. I then ran a optional direct cable which probably has better sound quality but I still miss the (no longer used) remote device which showed what was always playing on XM radio.
Since then, I also bought the Delphi XM radio boombox with home adaptor and another car adaptor (FM modulator) for my other, weekend cruising car (and yes, another XM subscription too but better combined rate).
Once you have it, you'll never listen to normal local radio again. It's nice too when travelling as you can always find decent tunes anywhere you go even if you don't want to bring cds.
Gets worse.....I'll also admit that since having XM radio and listening to internet radio too, I've found many more cds to buy.