yes
no
if you can still work on that imac then work it, it is not very portable though 
anyway if you are in need for a bit more juice, i recommend buying a used one, starting with a graphics card with 2 gb of video memory, nvidia, radeon, that should hold you for the next 2-3 years still.
apple is in the process of changing the processor architecture entirely, with a new laptop probably coming this autumn, if not now with the new processors i am pretty sure it will not take more than a year till they put a completely new design out there, since apple actually hired a specialist a while ago. here is a bit info regarding the new architecture.
under the line i would at least wait a bit still or buy a used which keeps you above water for just a little longer.