Photoshop extended vs normal features missing and wanted

Last year I bought Photoshop CS3 - recently I found that even though I could do HDR etc the one thing I really wanted was the 'median' filter - ie the filter that displays the 'median' rather than the 'average' from a stack of similar images - very disappointed to find this is only available in extended - and another $300 on top of my already $200 (yes it was an update - though it feels like a downgrade).

Does anyone know of a way of getting around the lack of this feature, or a free software package that allows median vs averaging.