Looks like a nice setup. One note though - currently Moldflow can only utilize a single GPU so doubling up the Tesla cards may not give you much of a performance boost.
As for the other questions, the minimum amount of RAM depends entirely on the amount of elements you typically deal with and what types of analysis you plan to run. I have 8GB of RAM on my laptop which is OK for the work I do, but if you have models with millions of elements you will require more. For the hard drive, a 10,000 RPM SATA drive would perform nicely.