I've helped my Dad change a significant chunk of money going forward by moving his SIMPLE IRA from American Funds to Vanguard. All you need to do is make sure that your account is a 5304 SIMPLE IRA, and you can switch to another financial institution. If however, the plan is a 5305 SIMPLE IRA, you cannot switch.
Needless to say the American Funds had a 2.5% sales charge on the front end, approx. 1% management expense ratios, $10 annual fee, terrible fund offerings, and a terrible website over to a Vanguard account that will be invested in the VTSAX with a 0.05% expense ratio.
