1. The $450 is for the adaptor, to get a CHAdeMO installation figure about $15,000 plus installation--assuming you can even get it installed at your house.
2. While twin chargers are a nice-to-have, and when you need one on a trip you'll be very glad you have them, for home charging it's not necessary as the HPWC can be set to 40 amps. Note that if you go for 80 amps you'll need a 100 amp circuit breaker which, in many houses, means a serious panel upgrade and perhaps a service upgrade as well. Now that they are no longer a high priced add-on, you can get one installed anytime before a trip where you need it. (Be sure to order well in advance in case the Service Centre is busy)
3. A NEMA 14-50 works too and almost never requires an upgrade to your electrical panel or service.