Tire size for Style #87 wheels?

[varun]

I am looking to get some new wheels for my 2006 X5 4.4 sport and have been unable to find any original BMW #87 wheels for sale. Hence I am considering going with the replicas as seen here.

http://cgi.ebay.com/ebaymotors/20-In...spagenameZWDVW

Couple of questions.
1) Is this a good price for replicas?
2) What tire sizes will go on this staggered setup? I am told 275/40/20 in the front and 315/35/20 in the rear. Those rears seem awefully wide!
3) Will this be a lot worse for gas mileage?

I would rather go with the same wheel and tire size all around so I can rotate. Can I have the 20x10.5 wheels all around with 315/35/20 tires, will they fit with no rubbing issues? Could be an agressive look with those wide tires all around.