Though I have not heard a CT-5 yet, I'm pretty much in agreement with Chuck and Oldfogey re the 16LS. And the latest CJ power cord that comes with the ACT2 (and Premier 140) is probably the best stock cord I've heard. (16AWG, 10ft., translucent H-grade plug) That's not to say it can't be upgraded, I'm sure it can, but for me its partly a matter of diminishing return.
Where I've heard the 17LS, 16LS and ACT2 each benefit is from a Shunyata Hydra, with the 17 taking the greatest relative improvement and the ACT2 the least. But definitely all reap real gains, which, in essence, is a lowered noise floor. That gets cashed out as revealed detail, blacker backgrounds, cleaner separation of leading from trailing edges, etc. For my experience I'd do a Hydra audition before I'd look at power cords.
If you do try different cords, let us know what you discover. And, btw, how do you like your CT-5?
Tim