Yup, I went with 17s and 205/50/17 tires to stay as close to stock weight as possible. Wheels start getting heavy past that unless you shell out big bucks. Those Infinity 19s look really nice but those G35s also have big V6s. Wheel weight isn't as critical when you already have 300hp.
Also consider that that guy was riding on tires that were too tall for the xB2. That will make your odometer read fewer miles than you have actually traveled. So he probably didn't really lose 55 miles/tank, but I'm sure he lost some mileage.
I got hub rings with my wheels, but I also just bought an extra set off eBay. as long as you know the hub bore of your new rims, then you're set. For example my rims' hub bore is 73mm. The hub on our cars is 60.1mm. So I have 73-60.1 hubcentric rings. The plastic ones are what people like because the metal ones can seize up to your hubs.
I got these:
eBay Motors: HUB CENTRIC RING 73-60.1 LEXUS ES IS GS LS SC RX (item 160308882498 end time Feb-07-09 09:13:29 PST)