There may well be a need for extra RAM, not because of FL itself, but because of other subsidiary programs and background tasks such as antivirus, anti-hack systems etc. Also, the more slots are filled, the more memory bandwidth your computer has to allocate to programs requesting some. Even if all the memory is not allocated, the programs may be hitting the bandwidth limit of that particular stick, limiting it to processing below its maximum capacity.
Hope that made sense, but:
More RAM sticks = More RAM bandwidth for faster storage and access of memory. You may well find that you see a responsiveness increase (ie, decrease in response times) with more RAM bandwidth. Also, fast CPUs can be stifled by a lack of memory bandwidth, as the core does not cache the data it processes fast enough, because there is a queue.
For gaming, 2 GB is required for any higher end game. For a server, the benefits are mostly to do with bandwidth, and the amount of data being cached before being sent to their destinations (mostly in other countries).
Im not saying that you should purchase either a new CPU or more RAM, because the server is pretty good right now. Im just pointing out that there's more to RAM than temporary storage.;).
