a park_joy_2160p.y4m http://media.xiph.org/video/derf/y4m/2160p/ with a current x264 git pull encode down to 720P might be interesting to use for generic bench too etc.
now that Zacate and Ontario were officially released as of 01/04/2011 it seems AMD made another boo-boo by including all the usual FP operations (upto SSE3) but not AVX especially now AVX assembly is in x264
Sat, 15 Jan 2011 18:44:45
Add AVX functions where 3+ arg commands are useful
remember that the real life SIMD/AVX integer results are what x264 uses in its code not FP SIMD/AVX operations
and soon enough ported to ffmpeg/libav if only the developer could get a board to play with.
in the case of ffmpeg-mt that's primarily Alexander Strange "astrange",
and in the case of general SIMD you already know them from the directly linked log's above.
as for the developer of the AVX functions you should already know given that you have been running code profiles apparently, that's Daniel Kang the 17 year old kid that came to x264 IRC under the goggle code in task's a few months ago knowing nothing about x86/64 SIMD/ AVX assembly and yet ended up writing these very same routines your seeing such an improvement in many 8/10bit encodes code profiles etc.
so he's not really up for paying out pocket money for even a cheap Zacate board and case etc not that it would help new active and prolific developers like him in adding new AVX and related SIMD assembly code to x264 etc in timely manor , never mind up for buying a AVX capable quad or better AMD/Intel board and everything else to make a working and productive developer any time soon... and cant even participate in the current goggle summer of code to get receive the stipend to help pay for any future kit as he's not old enough yet, even if he is the current star pupil of both x264 and ffmpeg/libav developer's.
you would be well advised to sponsor him and the other students in your own small private (one off ?) AMD summer code-in sponsorship right now totally separate from anything else going on in the Gfx land and get a massive return in your investment in a few months or perhaps even less depending on how well they do for improved video encode/decode for everyone to enjoy and advocate in the future and given some breathing room for your other projects to materialise etc.