Oh man, I stumbled onto this thread too late. It took me about 20 minutes to replace (upgrade) my SM-RT800 rotors with some Dura-Ace level RT900 rotors that I scored a sweet deal on, and also to replace the resin pads. The resin pads cost me $40, and the rotors $100, and although the 800s were still very much within their lifespan (this was a "coolness" in looks purchase) but now I have some 800 rotors to fall back on once the 900s wear out, until I can purchase another set of 900s.
I did not realize I needed to have unlimited funds, a Gold Card, and to crawl to my shop.
Silly me thought all I needed was some hex keys, a couple of inexpensive bottom-bracket adapters to my torque wrench, gloves, shop towels, grease and isopropyl alcohol, an internet connection to watch a couple of YouTube and Parktool videos, and a can-do attitude. I had most of the tools already because I like working on my bikes, the only real outlay was the bottom bracket adapters, which together were $40.
Oh, while was doing this, I also flipped the front brake caliper mount to convert it from 140mm to 160mm for extra stopping power.
100 miles over 3 days of riding on the new brakes and they work great, totally quiet, and look awesome.