XM Weather is it's own subscription seperate from your Text services such as PDC and ATIS.
XM Weather Aviator is $50.00 a month. We recently switched to ARINC for a flat fee that was much less than Honeywell GDC or Universal (both of which were killing us with charges for stuff we were not requesting).
As a word of caution. When you first switch providers there will be some overlap. You will still get your ATIS and text just fine, HOWEVER you will be on both provider's PDC list (Universal and ARINC for instance). This will cause the FAA system to dump your PDC. Clearance will get the request and issue you a PDC, but when it goes back through the FAA computer system it will get dumped. It will take about 2-3 weeks to sort itself out as your old provider takes you off their list (sometimes they forget or try to make their competitor look bad and you have to wait another cycle - PITA). I have been happy with ARINC. You can still use Universal to file Oceanic clearances and get them to download the route through the FMS even if you have ARINC as your provider. Same is true for domestic flight plans, although I use fltplan.com exclusively and that is not an available option with them (but it's free and user friendly and support is great).
