I had a similar dilemma when I bought my 335. I originally ordered it with business nav then got rid of media all together and got other options instead. I'm no expert in any of this but, 2k is a lot of money especially when on a day to day basis you'll never use it. The basic iDrive system will be more than enough for an every day user. All depends on your circumstances but baring in mind Google Maps on iphone is more up to date, more accurate and just generally better than any other system, I really can't see the need for in built sat nav. Unless you use it everyday in the car.
Just my personal opinion. You can buy the professional nav system off eBay in good condition for £500-700 including the GPS aerial. That's if you get desperate and regret not speccing it.