Great advice Marvin...thank you for that!
For me the bottle neck is GPU..I think...I am OK with render times but screen redraw during the design process can be irritating. I use C4D BTW.
It doesn't seem to be a huge speed benefit from the i5 to the i7( late 2013) as you pointed out compared to what I have now...I think:)
A macPro...would be amazing but not in the cards $$ wise
If I could sell me Imac now for 1300 and then have to put in another $1000 to get a new one...