I have the Chi Vitalizer, probably I have had for 3 years I guess. Always liked it.
MH thinks I am lucky because he says often they don't last that long.
A year ago I also got the Chi Superdeluxe Evergain, I wanted to try a neck unit.
I ended up only using it for the legs. I found it kind of scary to do my neck, it felt unnatural and already had neck problems. MH says it is good to do your neck.
I bought mine at http://www.allaboutmassagers.com
this same company owns other companies too but I forgot the names, the prices might be the same.
They often have sales, that is when I bought.
Edit: Just checked the website take the retail prices with a grain of salt, they always run more around $200, I have the feeling I paid $229.