Help me compare 2 configs for my wife's new car (320xi vs 328xi)

We plan to do European Delivery in June 2013 and with the new 320xi out I am a bit undecided what to buy.
It will be my wife's daily driver (I will drive it once in a while) and she is not a spirited driver but likes the size and look (so I get to decide on everything but the colors). She is currently driving a 2011 328xi.

If I compare on MSRP basis here are the options that seem to make sense for her (we are in Colorado). The car will be a 3 year lease.

Car 320xi 328xi

Base 34550 38850
Melbourne Red 550 550
Black Dakota Leather 1450 0
Silver Matte Trim 0 0
Cold Weather 950 950
Driver Assistance 950 1900
Premium Package 3200 3100
Fold Down Rear 475 0
Destination 895 895

Total 43020 46245
Invoice ED (est). 37400 40095

There is a difference in the driver assistance package (blind spot and more cameras) so I understand it is not fully apples to apples comparison. But those 2 things were not really on the list anyway (was mainly looking for the park distance).

Couple questions:

1. anybody sees any errors in the math above ?
2. For her the 320xi seems to have enough horsepower so not sure what else I would get in the 328xi (if its my car I would get DHP but I doubt she would use it or notice)
3. I don't see the point about Nav, she uses her current Garmin maybe every 2 -3 month, also we got like 3 Nav systems on our iphones (Waze, Google and Apple). I have it in my car and it is nice but a lot more money then any good Garmin.
4. Anything you would change on the options and packages ?
5. Any idea about money factor and residual differences ?
6. Is the 328xi worth the 2.7k in this configuration ? Main difference I see is the higher tuned engine (seems to be the same one otherwise)
7. any other feedback is welcome

thanks for your help