Как я могу центрировать содержимое ComboBox по вертикали?

. Например, обратите внимание, что текст не совсем по вертикали центр ComboBox.

Вот мой XAML:

<Window x:Class="_24HoursBook.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="450" Width="350" MinHeight="450" MinWidth="350">


    <Grid ShowGridLines="True">
        <Grid.RowDefinitions>
            <RowDefinition Height="0.15*" />
            <RowDefinition />
        </Grid.RowDefinitions>
        <Image Grid.Row="0" Stretch="Fill" Source="Image/topBarBg.png" />
        <StackPanel Orientation="Horizontal" Grid.Row="0">            
            <TextBlock Text="Platform" 
                       Foreground="White" 
                       FontFamily="Georgia"
                       FontSize="15" 
                       Margin="10"
                       HorizontalAlignment="Center"
                       VerticalAlignment="Center"/>
            <ComboBox x:Name="cmbPlatform" 
                      Margin="10"
                      FontFamily="Georgia"
                      FontSize="15"
                      MinHeight="30"
                      MinWidth="140"
                      VerticalAlignment="Center">
                <ComboBoxItem>All Platforms</ComboBoxItem>
                <ComboBoxItem>Playstation 3</ComboBoxItem>
                <ComboBoxItem>XBox 360</ComboBoxItem>
                <ComboBoxItem>Wii</ComboBoxItem>
                <ComboBoxItem>PSP</ComboBoxItem>
                <ComboBoxItem>DS</ComboBoxItem>
            </ComboBox>            
        </StackPanel>
        <Image Grid.Row="0" Source="Image/about.png" 
               Height="16" HorizontalAlignment="Right"
               VerticalAlignment="Center"
               Margin="0 0 10 0"    />

        <ListView Grid.Row="1" Background="#343434">

        </ListView>
    </Grid>
</Window>