The "highest performance" is pretty subjective considering you haven't really provided much information to go off of. There are a lot of dependencies on this like:
- How much traffic does your site get or do you expect?
- Are you utilizing Kentico caching to the greatest extent?
- Are you using Dynamic Compression?
- Do you have any custom code? Is it optimized to use caching?
- Have you followed the recommendations for optimizing your website? (google it, several articles by Kentico, MVP's, etc.)
It's really hard to recommend when there are so many variables.
The minimum I use for a moderately visited site (20-40k visits per month) is something like below:
NOTE: Always split web and database servers off for high availability, performance and security reasons.
- web server - Windows Server 2012, min 4GB ram (8GB better), minimum 8 core (2 sockets, 16 logical processors) Xeon CPU 2.0 or higher processor, 100+ GB solid state drive
- database server - Windows Server 2012, SQL Standard (no CPU or db size limitations), min 8GB ram, minimum 8 core (2 sockets, 16 logical processors) Xeon CPU 2.0 or higher processor, 200+ GB solid state drive (size dependent on your db size and backup policies)
Keep in mind, the more caching you have the more ram you should have.
Having a load balanced web farm will help will performance if your site is overloaded so not sure why you're voting that out. Although if you have a static brochure website with little traffic, all of the above is pretty much overkill.
I'm not saying these are locked in stone and should be use all the time but they are what we recommend to our clients for the sites we build (which range from brochure websites to highly integrated websites with many different processes running at any given time). Check out the Performance Test Report. It has configuration of the server(s) as well as the results, very good information.