Your expectations are not in touch with reality, while you could do it doesn't mean you should.
To expand on Brian's comment: being able to have 10K concurrent calls and 500cps on a single box may be a complete awesome feat but that doesn't make it practical. I may have a race car that can top out at 250mph but that doesn't mean I should drive it that fast when cruising around town.
If you have a business case for that many cps and concurrent calls then you're better off not putting all your eggs in one basket and instead scaling out horizontally. The last thing you need is for all 10K calls go down because of a server hiccup!