Number of Users and Processing Power

With being told that 50 users on a 1 gig ram, 2 CPU cores, VPS could bring Dolphin to its knees, just what is the numbers vs processing power?

How many users could simultaneously be online with a dedicated server with 16 gigs of ram, six core CPU that is going to run centOS 6 64bit, the Apache Server, and the MySQL server?  We have already been discussing moving the MySQL server to a dedicated box when we have the funds.

50 is really too much for that 1 GB VPS but 16 GB dedi can take i think around 150 users (i think, what others think?) without overloading the server. Of course its just an estimate and realty could be very different. If you move to cluster than your site could work lot better in heavy load. I will recommend nginx if you think you can manage with it.

Could be 500, Could be 50000

static content/site will use less
dynamic content/site will use more
install all the modules and it will use more

http://www.boonex.com/trac/dolphin/wiki/TutorialHowToCalculateLoadAndHardwareRequirements#Howtocalculateloadandchooseproperhardwareforwebservers

30 (average seconds per one request from one user) / 0.5 (our average "Time" value) * 150 (simultaneous requests) = 9000 online users

1 (average seconds per one request from one user) / 0.5 (our average "Time" value) * 150 (simultaneous requests) = 300 online users

http://gtmetrix.com
a good place to start to optimize your site.