iMac 21.5"

[stespin]

hello,
I'm thinking about buying the iMac 21.5" with this specs:
-Intel Core i5 quad-core 2.7GHz (maybe you'll tell me if the i7 works better for what i need to do)
-4 Gb Ram (again, if 8/16 Gb is better just tell me)
-1 Tb Hard disk
- AMD Radeon HD 6770M 512 Mb

I am an italian architecture student, i have always used AutoCad, ArchiCad for 3d and i am quickly learnig to use Artlantis for 3d rendering. Now, i own a Dell laptop wich is quite new (like 1 year old) but i think that i'm working too much on it: extreme heat (you could really hurt your hands touching it), it often crashes and sometimes even AutoCad is really slow when using some functions. I am quite a heavy user because when i'm under exams it happens that i work on both Archi and AutoCad for like 15-17 hours a day. So i thought about the iMac.
is the one i told you above enough for what i need to do? or the 27" would be better?
P.s. sorry if my english isn't perfect, hope you'll understand anyway my "problem" XD

 

[spy008]

I'd go i7 and you should be able to pick up 2 4gb sticks of ram for about $50us(don't upgrade thru Apple). Alternately you can get 4 4gb sticks for a total of 16gb of ram for about $100us(supposedly you can go up to 32gb of ram in the iMac). 1tb is good but if you can afford the 2tb HD then go for it. I run Mastercam under parallels w/12gb of ram and it's awesome.