Dell has a strange website. Last time I was looking for a model with lots of RAM it took me ages until I understood how to get to the part that lets me configure it freely.
I agree, they used to have a configuration page where you built up your PC,now you get to scan through what they offer as canned configurations. I totally dislike it, especially since they have different sections and you have to go to each a scan for the config your looking for (and the price of course).