You have four 64-bit, 24GB servers, with 16 cores each with which to implement SharePoint. I know there are some variables here, buit how well do you think it can handle 1000 users. How many users can it handle? Intent is to ultimately replace 90% of file share functionality. which has 1TB of data.
I've intentionally left storage out because it can be expanded upon overtime. History shows me the other things are much harder to get "approved" for expansion since the case to be made for expanding things like processors and memory tends to be more subjective (vs storage with either "IS" or "ISN'T" running out). Assume RAID 10.