Hello @japsas100,
excellent question. Specially since you are installing a distributed version of SAS Visual Analytics and, therefore, the stakeholders will be closely looking for the best performance, I would get a good sizing proposal from SAS (from the SAS Excellence Center - EEC) by contacting directly your SAS account manager. And surely I would not take any advise from external parties, even if they are based on experience (of course those advises can be taken if performance and reliability are not priority 1 concerns. After all, they are your systems/servers).
Here I would like to share with you a good post created by @MargaretC, explaining the reasoning and indications to get a good quality sizing, plus how the whole process work, on simple words. http://blogs.sas.com/content/sgf/2013/11/27/sas-deployment-whats-the-right-size/
I hope it may help you.
Kind regards,
Juan