Laptop hardware component & upgrades forum: Need Opinions/Advice On Laptop Hardware

Hello everyone. I plan to purchase a laptop in the near future that i plan to use for gaming and designing stuff in autocad (2d and 3d). The laptop that i plan to get is the Asus VX7.
http://www.xoticpc.com/asus-vx7a1-lamborghini-p-3044.html?wconfigure=yes
The hardware that i need advice on are the CPU and the RAM. From my understanding, correct me if i'm wrong, the more GHz a CPU has the faster/better it performs. Though i'm not entirely sure how much better. The other thing i dont completely understand is the CPU cache. Here are the choices i have for this laptop (the + at the end is additional cost):


2nd Generation Intel Core? i7-2630QM, 2.0-2.8GHz, (32nm, 6MB L3 cache) - Standard (Does not support DDR3 1600MHz Ram)


2nd Generation Intel Core? i7-2720QM, 2.2-3.3GHz, (32nm, 6MB L3 cache) (+389)


2nd Generation Intel Core? i7-2820QM, 2.3-3.4GHz, (32nm, 8MB L3 cache) (+569)


2nd Generation Intel Core? i7-2920XM, 2.5-3.5GHz, (32nm, 8MB L3 cache) (+1,089)

so i need opinions and advice on which to get. obviously keeping the "bang for your buck" aspect at its best. The 2 i'm mainly considering are the 2720QM and the 2820QM. Only differences are 0.1GHz and 2BM of L3 cache. Is that difference worth $180? is it even worth upgrading to either of those and better to keep the standard one?

My second area of advice would be the ram. The obvious fact is that the more RAM you have the faster the computer is. 8GB of ram would clearly outperform 4GB of ram. The thing that i dont understand is the differences of frequency. These are my choices (with additional price on the side):


16,384MB (16GB) DDR3 1333MHz Dual Channel Memory (4x4GB)


16,384MB (16GB) DDR3 1600MHz CL9 Kingston Hyper-X Dual Channel Memory
(4x4GB) [Pleae Review Laptop Specs for Supported Memory Speeds] ( + 250 )


16,384MB (16GB) DDR3 1866MHz CL11 Kingston Hyper-X Dual Channel Memory
(4x4GB) [Pleae Review Laptop Specs for Supported Memory Speeds] ( + 325 )

the only differences between these, to my understanding, are the frequencies. 1333MHz, 1600MHZ, and 1866MHz. Would upgrading to a higher frequency make a large/considerable boost to performance? considering the prices are 250 and 325, i would keep the standard if the difference is small.

i would appreciate any help. this laptop is going to cost me more than $2,200 so i want to make sure i do it right. I would also obviously take into consideration other laptops that offer better specs for the same/lower prices. thanks in advance! (ps, all prices of upgrades are in US dollars $)