"There are some computing tasks that can't really be split up among multiple nodes, so they still require gigantic CPU requirements. Usually this is related to legacy databases which cost less to keep on the legacy architecture than spend the time to try to move it to PC clusters."
True but what does that have to do with the usage of Power/Sparc? There do exists 32 and 64 processor xeon systems, and sgi will even sell you a system with 256 cpus and 64 TB ram if you can pay the price.
Let me quote "SGI UV 3000 scales to extraordinary levels - up to 256 CPU sockets and 64TB of cache-coherent shared memory in a single system."