Help. Want a bigger tank !!!!

Hi guys, I really need some help, I have a 130 litre tank, and I really want a regal tang, badly, but I know this is to small for the tang, i am going to upgrade soon to maybe a 400litre tank and want to know if it's better to buy the tang now and place in tank I have now, deal with the ich problem with the tang then place in bigger tank when I set it up in month or so,?
I have been reefing for 5 years and love it so I'm not new to it all

Thanks