Looking at purchasing a 3 series

[jay_vw]

I'm in the market for a new(er) car soon. Was considering a 2006-2009 3 series with the x drive. What sorta things should I watch out for, are there any reliable issues with the different years/models or maintenance items that need to be done by a certain mileage? I know the specs for the 328,330,335 just curious if any of those are better or worse. I do like the lines of the coupe more, but unsure how much that back seat is useable space. As I have a 5yr that will be traveling in it, I hope to drop by a dealer shortly to see. What I would like is one with navi, but I've noticed that they are hard to come by. One thing it MUST have is a manual tranny.

Thanks in advance