My 401(k) plan, to which I make after-tax contributions, has excellent choices for index funds. I have a plan to get Admiral shares of Vanguard Total US Stock Market (ER of 0.06%), then use the bond fund and international index fund in my 401(k) (ERs of 0.04% and 0.14%) to round out my portfolio. I am trying to optimize my portfolio such that my blended ER is less than 0.1%.
I don't have enough in my IRA to afford Admiral shares ($10k min investment), so I was thinking of moving money from the Roth 401(k) to the Roth IRA to do this. Is this possible? I've only seen rules for moving money from a traditional 401(k) to a Roth IRA (and in that case I wouldn't be able to pull this off), but I think this situation is different since it's after-tax cash in all cases.