As per Zell's recommendation to post the results, the following's a test I ran using Derp's Episode 02 OP passage:

Intel i5 760 (2.8GHz, quad core, 8GB RAM), CCCP - no lag
Intel C2D E8400 (3.0GHz, dual core, 4GB RAM), CCCP - no lag

Intel C2D E6600 (2.4GHz, dual core, 4GB RAM), CCCP - LAG ( <-this PC used to handle everything that my laptop couldn't, including [Derp]_DenYuuDen OPs).

^ Same machine.........................................., CoreAVC - LAG (no lag apparent until towards the end of the OP, ~2:27 of episode 02)

AMD Turion 64 X2 TL-50 Mobile (1.6GHz, dual core, 2.6GB RAM), CoreAVC - LAAAAAAAAAAAAG
Conclusion: It takes a powerhouse to render those subs.

Note that the number of cores doesn't really matter as the decoding's single-threaded. The clock-speed and architecture (how new, and resultantly more efficient, the CPU is per clock) would play a bigger part. I don't think the i-series was that much more efficient than the C2Ds though.