Nope, as of now you cant use Dopus 5 with powericons. I would recomend giving Diskmaster II a try. Its a good file manager and its free. It doesnt have aworkbench replacementmode like Dopus 5 does, just a straight filemanager. If you want to use PNG icons, your just going to have to decide what you want more. Dopus or the new looks.
On a side note. This goes with MorphOS users too. You cant use dopus since MOS uses PNG icons as well, but if you use the old icon lib from OS3.x you can use it.