The problem is, based on several cases we've seen so far, if you apply right now without any bank statement history, then most likely they will immediately ask for bank statement history several weeks after PER. So you never know, they could ask, say, in 3 months time, then your bank balance would be less than the threshold for three months and they will see the deposits to your bank account three months ago.
The best is to transfer now, wait 6.5 months, then send the application along with bank statement + 6 months history, which shows that the money has been there for over 6 months, and no large deposits can be spotted within these 6 months. But obviously, by June, the cap could've been reached, and by next year, they could've cancelled the PhD stream (God forbid), so it's hard to say really. If you have a bank statement under your name in your home country, which has more than the required threshold for over 6 months, it's probably best to use that (and not touch the money until you get your PR), and apply now.