I'm afraid you can't. Even if you buy ScriptVocalizer Agency without the Standard Version and even if you buy without the Standard Version you will not be able to login.

Here is why:

1. ScriptVocalizer Standard is the main product which is either an Yearly Subscription or Monthly Subscription.

2. ScriptVocalizer Agency is an Upgrade or Up-sell  which adds the Agency features in your ScriptVocalizer account.

3. Since ScriptVocalizer Agency is not independent, you will need to subscribe for the main product ScriptVocalizer yearly or monthly subscription first. Else you can't login with only ScriptVocalizer Agency in your account.