Don't know your $ thoughts or not but TSS Radio has the SR903 for only $60...maybe you get it so you know you have a good sat tuner and cable to eliminate that part and if it still doesnt work return it knowing it is your head unit.
http://www.tss-radio.com/products/ke...te-radio-tuner
Although you would have to go talk to Sirius to change your ESN...but I do know folks who have called Sirius in similiar situations and Sirius would swith you to your new ESN so you could test without charging you the "transfer fee" or whatever they call it unless you find out for sure it is the tuner.