525d and 530d will protect you best as the 535d's are still holding their value very well but will cost you a lot to own. I think the 530i is a great car too, lovely engine and not bad fuel consumption and can be had nearly new for a solid saving which may outweigh the saving a diesel car would give you. As far as I am concerned their is not a bad 5 series, its levels of excellence really.
I would urge you to drive a 525D and 530D and also a 530i in Sport guise. Options wise I always say the same, buy the bits you need as you virtually NEVER make the money back on the options you spec, but if buying second hand buy the car with the most options for the best price, which is obvious.
More options make the car easier to move on, but if you plan to trade it to a dealer it will be of little relevance other than you may get more for it, but this might be less than you paid to have the options in the first place. Options are an opportunity for dealers to make money. I was told never buy an E46 M3 without Sat Nav, and I bought 2 with out it and didn't loose as much money as those who bought Sat Nav!
Tis a buyers market out there right now, LOADS of solid deals to be done and solid discounts of sticker prices if you push hard enough.