AD: Would be nice.
4+ Cores are coming to a lot more machines soon. Intel's upcoming
Nehalem architecture (due later this year,) will have 4 cores in 'mainstream' mobile and desktop chips; and 6 or 8 cores on the high end workstation/server. (Meaning the Mac Pro will be a 12 or 16-core system.) Plus it brings back Hyperthreading, so those 4 cores will appear as 8. (And the Mac Pro's 16 cores will appear as 32.) Only the low end chips will be 2 cores. And even those will appear to have 4 to the OS.
iMacs all have discrete graphics. Only the MacBook and MacBook Air have integrated. And regardless of the discrete graphics being "weak", they can still do some tasks better than even the upcoming Nehalem CPU. (And, all currently shipping discrete GPUs in Macs have unified shaders.) As for accelerating video encoding, I had a $50 PCI (not PCI Express) Radeon X1300 in my son's computer, and it did a very good job accelerating video encoding using ATI's provided software. It made the 3.2 GHz Pentium 4 (single-core,) nearly as fast as the CPU-only encoding on my 2.0 GHz Core Duo. (Which, for all other CPU-bound tasks, was more than three times as fast; beating out a 4.0 GHz dual-core Pentium-4-derivative on many tasks.)