number of cores depends on how many users you want to service at the same time and if you want to do media caching. try it with at least 4 cores. as for memory, with 16GB RAM it should work fine, 32GB is what i usually suggest as it will have more opportunity to use disk I/O cache and since you probably have some other processes running on the server. for storage, after 6 months and 125mil events, our database is around 330GB. but i could prune older events and reduce storage requirements if you dont want to archive everything forever.