There's no way to accurately answer this question as it depends on a huge variety of environmental factors. As an example, processors are varied. Even within the same processor Family/Model, there can be significant differences between them (IE 2.0GHz vs 3.0GHz), or cache, power states, turbo modes, etc. The best way to estimate what you need for your environment and your goal of 9 tiles is to take several data points at lower tiles.
For instance, if you ran the following data points:
1 Tile consumes 10% of CPU, MEM, DISK, NET
3 Tiles consume 32% of CPU, MEM, DISK, NET
7 Tiles consume 74% of CPU, MEM, DISK, NET
then you have a reasonable expectation that you could run 9 tiles before saturation (but this is not a guarantee as you could hit a bottleneck along the way).
If for you had run 7 Tiles, and it was consuming 93% of CPU, MEM, DISK, NET then you it would be much less likely you could run at 9 tiles without adding more resources (like an additional host).