Question about PC to PS3

[Niwashi]

You can use your current account on both platforms. You'd need to (as you mentioned) buy a PS3 copy. The first time you run the PS3 version, there will be an account setup step before it starts, asking if you have a current account or want to create a new one. Just make sure you log into your existing account at that point, so the PS3 version is linked to the same account you've been playing on PC. That will both give you access to your current character(s) and give you whatever playtime remains on your account. Though the initial game purchase has to be made for each platform type, there's only a single monthly subscription fee for the account, regardless of whether you have it on multiple platforms or not.

EDIT:
Oh, and since game purchase comes with 30 days of subscription time included, you'll get another 30 days added to whatever you already have now, once you add the PS3 purchase to your account.