I second what MalcomDiggs has said, but run some benchmarks on your home box with all the memory. Find an amount at which performance increases level off, & request a just amount based on hard data. If they don't respond after making it perfectly clear as to what you need to do your job properly, then leave. (Assuming you can easily get work elsewhere)

Maybe link this comments thread in your intranet post, a community like HN expressing sane norms might help your case.