HELP! Graphic Design workstation 12GB + DDR3 RAM

Hello All!
i am new to this site, and this is my first post. i am looking for honest opinions and suggestions for a new system i would like to put together for my business. i own a graphic design and print shop. i do alot of vehicle wraps and large format printing. with that being said, i need something that can handle large file sizes, with low or no slag time. currently i am working on a system i had put together four years ago, come this december. it runs Windows Vista 64bit, Intel Core 2 Due CPU @ 2.4GHz with 8GB DDR2 RAM. when i first got it, i did think it was much quicker than my previous system, but still found it slow for having this much ram. simple things like opening Outlook, would freeze things up. when i create a wrap, i will do the vehicle or project at full size, if allowed to in Photoshop, but at 72dpi. so, i work with 1.5-2GB files all the time, and right now, it flows, but like i mentioned, it seems slow for this much RAM.

so, i would like to get a new system soon, and wanted to upgrade to the newere DDR3 RAM. i would like to go to 12GB +, but have heard pros and cons on this. i have also heard how having faster hard drives helps with Photshop, but i have never really been told how or why. i have no clue what "cache" is and a lot of the other terms with these things, so i appologize for asking a dumb question if taken that way. i am trying to learn more about the system i have and what i can do to better a new one. i have no clue about latency, motherboards i should select and what to look for in RAM that will last the 16+ hour workdays that i endur, at least six days a week. i don't do any 3D or model rendering, no annimation. the only time i have to render something, is when usuing Genuine Fractals or a Photoshop filter. can you guys/gals advise me to what kind of processor, RAM, hard drives, power supply, motherboard, etc...... i should consider, to get me the fast and most efficent system i can for what i need it for. i want somethign blazzing and dosent freeze up like this one i have now, especially on the smallest of things i could be working on. this system now, also takes a good 5-7 minutes to load up everythign, kind of like it has to wake up in the worning first. if you have questions for me, fire away, i will try and answer them the best i can.

thanks

Professa