I am not sure why you would need another one unless one was for work and the other pleasure.
I had a SK2 and it was junk compared to my 7100i. Browsing was horrible, using the phone was a pain in the arse. I honestly think the SK series is a joke that has been made popular by the stars. Little do people know that they got them for free.
For One, I have needed to seperate Work and Personal as I used to have BIS mail come to 7290 aswell, I don't mind Personal Mail at all hours, its work that sometimes did not stop, also had customers calling after hours and weekends....enough is enough sometime's. For Two and Most important, I carry two for the same reason I own the Crackberry domain name local to my Country Top Level Domain.