How did I miss this post for so long??? Two of my favorite's, stereos and tractors!!!
If I had a cab, which I don't.....yet..... I would get whatever quality name brand (pioneer, alpine, kenwood, sony....etc) was a good deal, had USB in, AUX in, or even and iPod control system like Alpine's iPod full speed (although farting around with your iPod is probably the last thing you should be doing while running your machine). A lot of them now have dedicated SAT radio ins too. You can get pretty good speakers, pretty cheap. Often in the clearance bin (not returns, just blow-out deals).
DO NOT bother with a bluetooth thingy to connect your phones, the person you're calling won't be able to hear you over the engine.
My only advice is anyone is looking to SAT would be to go with SIRIUS over XM if there are any concerns over reception. SIRIUS runs 3 satellites, XM runs 2. I'm in the Rocky Mountain part of western Alberta and have lost signal only once tucked way back in the mountains sledding. Buildings and shelters still do it, but you'll have better reception under trees, etc with SIRIUS.
Have fun with it!!
-Jer.