Just an FYI - please be aware that an 8 hour train trip DOES NOT equal an 8 hour night of sleep. Train personnel will be by around 11:00 to collect your passports for the evening (assuming your train departs on time), and you'll be awakened around 5:00 for breakfast. This train also makes 9 stops along the way...If you're lucky, this equals a MAXIMUM of 5:00 hours sleep. Most people are lucky to patch together 2 hours :-(
Before I spent $500-1000 for a night on the train, I'd try really hard to see if I couldn't spend a night along the way and split the trip up into two day trains; I'm looking at Bolzano. go see Otzi ;-) Bolzano would be a change of scenery from Florence and Munich; if you can take more time, go farther up into the mountains. This would be closer to around 75€ pp, depending on your choice of train, plus a hotel for the night.
Whatever you do...DO buy the train tickets online ASAP! the discounted tickets are fading.fast. DON'T use Rail Europe! Use Bahn.com and Trenitalia.com.