Glad to hear things are running good
Good luck on this project as well! As mentioned, it looks like your apps are using more CPU than I would generally expect, so the faster CPU might get you further than the faster disk. However, given the amount of system CPU I would definitely get the output of iostat -x and a vmstat for some time during your busy (cronjob) periods.
4GB RAM looks to be just about right, given the amount used for filesystem cache.