On December 29 I applied for a 1-year extension of my non-immigrant-O visa based on marriage. At that moment there was more than 400K on my account for a period of 3 months. I'll need to pick up my visa on Januari 29 2011 (appointment date).

From experience I know that the visa sometimes arrives a few days late.

On Jan 27 I want to pay for a new car (so 2 days before I get the visa) . Is it allowed to take the money out of the account before you actually get the visa?

I have always done so with no problem.