For some reason, XM is not yet offering true "a la carte" where you select only certain channels you want from a provided list. From what I have seen, all XM radios would be capable of this, since XM channel activation is done on an individual channel basis (you can even call XM and have certain channels removed from your radio if you find them objectionable). However, I think that the merged "Sirius XM" does not want people to be able to buy subsidized radios (sold below true retail cost) if they cannot charge a high enough subscription fee to make up for it.
Sirius does offer "a la carte" but only on one specific model of radio, which is only sold at a higher "non subsidized" price and therefore the company loses no money either way on the deal. Sirius' a la carte, in its cheapest package, does allow you to pick 50 channels from a list for $6.99 a month - the list is here
http://www.sirius.com/packages/alacarte - channels with a blue dot are premium and cost 25 cents each on top of the 6.99. No matter how many you add for 25 cents each, you will never be billed more than 12.95 under this option.
The XM package for $9.99 is called "Mostly Music" and Sirius also offers a "Mostly Music" for $9.99.
XM Mostly Music:
http://www.xmradio.com/onxm/full-channel-listing.xmc?tier=MM
Sirius Mostly Music:
http://www.sirius.com/servlet/Conte...id=1218563499691&pid=SIR_AUD_PKG_MM&catid=all
Both services also have a "News, Sports & Talk" package for $9.99.
However, neither Mostly Music nor News, Sports & Talk qualify as "a la carte" because they are still pre-set packages, and you cannot pick and choose channels within them.