Consider this code. I have not tested it but it seems sound.
PHP Code:
{assign var="varcharge" value="N"}
{if $product.is_variants}
{foreach from=$variants item=var}
{if $var.price gt $product.taxed_price}
{assign var="varcharge" value="Y"}
{/if}
{/foreach}
{/if}
{if $varcharge eq 'Y'}
From:
{else}
{$lng.lbl_our_price}:
{/if}