#2 - May 20, 2009, 5:15 p.m.
You're welcome to do both, actually. It's just a matter of which method is more convenient or compatible your life and game style. :)
My advice would be to begin with our Recruit-A-Friend program. From your main account, you can issue yourself an invitation. This invitation will contain a unique authentication key with which you can set up a trial account.
From there, you can choose to upgrade digitally or via boxed copy purchase. Again, it's up to you which you choose!
Here's some information to help you make an as informed decision as possible:
Please let me know if you've any additional questions. :)