Hey dude.. Don't change the stored proc.. Not a good way to handle it.
Look under Admin\EditUsers in your Project.
Part 1: Set your desired items in the list box as "selected" in the designer. Here's an example:
<asp:DropDownList id="dropSortBy" AutoPostBack="True" Runat="Server">
<asp:ListItem Text="Username" Value="0" />
<asp:ListItem Text="Full Name" Value="1" />
<asp:ListItem Text="Date Joined" Value="2" selected='true' />
</asp:DropDownList>
<asp:DropDownList id="dropOrderBy" AutoPostBack="True" Runat="Server">
<asp:ListItem Text="Ascending" value="0" />
<asp:ListItem Text="Descending" value="1" selected='true' />
</asp:DropDownList>
That's part one. Now, in part two, change the alphapicker default:
<community:AlphaPicker id="ctlAlphaPicker" Runat="Server" SelectedLetter="All"/>
That's all it should take. I've only preliminary tested this, but it looks like it works ok. No SP changes, no nothing!