A quick test, not by any means very scientific:
[10:01] * Tofu2 ササ MPClassic ォサ [||||||--------------] [DB L-E] Tsubasa Chronicle DVD version 01 h.264 [8C5BB019] ォサ 07:46 / 25:31 ォサ 768x432 ォサ 23.976 fps ォサ ~111.86KB/s ォサ 167.35MB ォォ X264
[10:02] <Tofu2> CPU Info: (CPU - Intel Pentium 4, 3.20 GHz, L2: 1024KB (20% Load))
[10:02] <Tofu2> 20% of a 3.2 Ghz
[10:02] <Tofu2> for 768x432
[10:03] * Tofu2 ササ MPClassic ォサ [|-------------------] [Live-eviL] Mermaid's Forest - Ep 13 (DVD) ォサ 00:59 / 24:12 ォサ 768x432 ォサ 23.976 fps ォサ ~166.58KB/s ォサ 236.36MB ォォ XviD MPEG-4 codec
[10:03] <Tofu2> CPU Info: (CPU - Intel Pentium 4, 3.20 GHz, L2: 1024KB (22% Load))
The xvid actually used 2% more CPU power to render than the h.264 for the same exact resolution.
20% of 3.2 Ghz is the equivalent of about 800 Mhz, so even a high PIII should be able to render it properly (unless your system is so full of spyware that you have no system resources left, in which case you have more problems to worry about
).
Anyway, all I am saying is, the idea of h.264 using an insane amount of CPU to render is a myth. It uses no more CPU than xvid :X
-Tofu