All in the memory!
For general office use an old Athlon x2 64 is totally adequate for your day to day needs.
It's memory which is the bottleneck on most office machines. Most companies still roll out laptops and desktops with 1GB of memory 2GB if you are lucky this is what really slows down productivity.
Add in a modern GFX (even a cheap one for £30) and you get good performance with modern browsers (thinking IE9).
Now build the GFX into the processor which AMD are doing, even with a lowly dual core or quad core and plenty of memory (64bit OS helps) and an office machine should last for years.
Workstations are a different matter, but they really only make up a very small proportion for standard business use.