135i:
Alpine White w/ Red interior preferably but dont feel the need to invest in leather (depends on leather/Premium Package cost)
Otherwise, Montego Blue w/ Beige leatherette (praying for some good leatherette choices)
Would love Dark Gray Poplar Wood
BMW Assist
USB Adapter (not sure if I
need this)
Definitely need Sport Seats if not standard (UK Brochure states that the 135i in UK Spec gets standard Sport Seats)
Upgraded Sound System (depends on how good the standard system is)
Power Memory Seats (if not standard and dependent upon price if optional)
Otherwise, nothing else is required, especially with the 135i getting all the performance equipment standard...
The goal really is to not spend more than what is absolutely necessary. However, somethings are much wiser to get done stock than go the aftermarket way (iPod connectivity, sound system upgrades, etc.)