typical BMW, confuse the hell out of the customer! Just remember the dealer is the LAST person to trust with the right answer
I have the 600 watt system in my X3 and its pretty nice. cost was $950 and included sat radio with 1 year subscription.
The X1 sound upgrade, if only to 340 watts and not including sat radio for $875 is a pretty big rip off.
I am guessing the 340 watt system is what you are getting. BMW should get their facts straight though, simple print out of the page showing 600 watts could get them into a lot of trouble in US courts,