CAS 2.0 is really tight for that speed. Not sure if I've seen 2.0-4-4 in combination before.

BTW, have you compared the performance difference between 1:1 and 4:5? I don't think running the memory faster than the FSB yields any gain at all when running in dualchannel. The NB-bufring will hurt latency, and the FSB will limit the effective throughtput anyway.