Satellite radio has made great strides in the past two years with many auto makers building it into car radios as another channel. Sirius promises to add 2.8 million subscribers this year, bringing the total of 6.2 million. XM Radio recently revised its subscriber guidance down from 9 to 8.5 million by year end. We had XM for three months free in a new car we bought in December, but did not convert the service to $12.95 month. After all, how many things can you listen in the car, satellite radio's primary venue? Will customers be willing to pay for satelllite radio month after month? Both companies have lost scads of money ramping up satellite radio and their stocks have been hammered in the past six months.