Unless you have a specific need or desire to go with larger, 20" wheels, why not save some money and stick with the factory 19x8" wheels and just go with a wider tire? The OEM 19x8" wheel come with 235/45 tires, with a 235mm width. You can fit up to a 255mm width tire on them and keep the sidewall ratio close as others have mentioned.
I went with the Michelin Pilot Sport AS/3+ at 245/45 on the OEM 19" wheels and they have been outstanding so far. They are no louder than the factory Continentals, no harsher, much more responsive, provide a great amount of traction, improve braking, and are very smooth running tires. Yes, they only have a 45K mile warranty and need rotating every 5K miles, but the handling improvement with these tires is amazing over the stock Continentels. The Michelins at 245 vs. the 235 stock have given me approximately .4" extra width on each tire so nearly 1" total extra tire width. I don't see a need to go to a wider 8.5" wheel when they will fit the same tire sizes.
Unless you are going strictly for looks with either a larger wheel or wider stance, I don't see a need with going to a larger, wider, and potentially heavier wheel when the factory wheel can be fitted with upgraded and wider tires that will far outperform the OE tires. Adding wider wheels may also require suspension modification as this will change your geometry.
Not trying to dissuade you, but rather I am curious as to why you are looking at wider wheels while using the same tire sizes that can fit on the OEM wheel?