I know this is a bit OTT, but in that stress test of yours, what is chewing up most of your resources? Cols? A.I.? Draw calls?
Draw calls = ~5%.
Using GPU-Z, my GPU usage is ~20%. Radeon 7950 (pretty mid-range these days).
Col isn't much, peaks around 700/tic, well below stress test col levels.
The bulk of the CPU use is for AI for target selection, priorities, movement for each ship (range, optimal firing solution, left/right shield facing against attackers, when to use missiles etc), drones & seeking weapons.
I have to limit the fleet sizes in encounters due to it being single threaded, since my CPU is a desktop i5-3570K, using more than 50% of that thread means a lot of people on notebooks would lag as their CPUs are lower clocked.
This definitely limits C2 to smaller scope games with fewer active AI &or simplistic combat.
If I remove drones (~50 drones), that same fleet battle peaks at 50% single thread load and ~35-40% average, well within acceptable range for it to run well on a range of setups. The problem is it loses the sense of epic-ness without hordes of drones. Can't have carriers without drones either. :/