Best I can tell, there are three XM modules available for my 2006 A6:

1. 4E0-057-593-A: This is the original XM receiver for my car, based on information in ETKA. I've found this receiver for as low as $94 on the web. It was superseded by ...

2. 4E0-035-593-A: Found this receiver on the web for about $350. It was superseded by ...

3. 4E0-910-593-E: Listed as the current receiver in ETKA. Goes for about $500 on the web.

My basic question is what's the difference? I believe that the difference between the 035-593 and the 057-593 is one came installed in the car (057) while the the other was sold through the parts counter (035).

At some point, it seems that most sat radio modules went from a dual antenna feed to a single antenna feed. My guess is the difference between the 057/035 and the 910 is that the 910 has a single antenna feed while the other two have dual antenna feeds.

Can anyone tell me with any degree of certainty whether I'm right or wrong? I'm going to buy an XM module to replace the Sirius module in my car and I'd obviously rather only spend $94 vs $350 or $500.

Thx
-K2