Lolz... Coded for 2 cores? yea right!
the OP wants to multi-task, so the more programs he runs, the more cores get stressed!
for example, take the case of a video converter(Xilisoft), when converting a single cip only 2 cores are stressed, but when you convert 2 clips together, all 4 cores get stressed. (You can watch it in task manager/within Xilisoft itself)
Basically, Video/Audio rendering and Games will take advantage of 4 cores. However 6 cores or an i7-2600 is realy an overkill unless u do loads of video/audio editing and rendering... or u use programs that will make use of 6 or more cores!
I am using an i3-2100 dual core hyper threaded to 4 cores..and got to say even 4 virtual cores(2 real + 2 virtual) Rawk...