You'll be happy with the 20" chrome. Those wheels on a black car will look aggressive, not Ghetto.
The 245/20 is an inch taller than the 245/19 and the rim will be at least 1/2 inch wider. So you just need to watch the offsets. Especially in the front. My 245/19 +45 comes real close to the suspension.
20x8.5 rim with less than +40 offset minimum.
Once you do it be ready, you'll want to lower it an inch or so, you'll want slotted rotors, nicer looking brakes, ...you get the idea.
I attached a pic of mine w/ 245/35R19 no drop. I like it but have plans this year for 20" chrome and 1.5 inches drop.

 

So.. what is the best offset for the 20s for our sedans... or 19s... and should u go with 245s all around the tires?...