19.5s aren't necessarily larger diameter and won't raise the vehicle height unless you want to. Even if true, 1 inch higher impact "described" in winds will be offset from the drastically stronger sidewalls.
$4-5K is high unless you went with the most expensive wheels and tires. In any case, I had a SRW because I couldn't make a DRW work for what I was doing.
I've never heard of any manufacturer voiding a warranty based on wheels/tires, but there may be one out there. GM might be it since they knew about an issue for 10 years and didn't (as has been reported) replace a $0.57 part. :)