more RAM will make the computer remember more stuff.
programs takes memory, so more and more programs require that you have the RAM needed to run it all.
so for multitasking it's great to have more RAM (as ohsnapworld said). but it also depends on what you are multitasking with. having 7 taps in chrome and running steam and skype does not take more then 4gb including the operation system. but if you did all that with a video being rendering in the background while downloading stuff, is something else. i have had a big video rendering + a big video converting + 4 taps in chrome + steam and other background apps like antivirus running with my 6gig RAM with no problems. so i think you will be fine.
other then that the computer use the RAM to remember parts of closed applications/tasks so you can open them faster next time. try to open photoshop and close it, then open it again and see if it was faster this time to open. i just did, and it was like 4x faster. if i wait 1 hour and keep on working then maybe it will only be 2x faster because of it is gonna use more and more ram, so it needs to get rid of more and more already stored data. the more memory it has the less data it needs to get rid of when you are working with other stuff.
Mhz on the CPU is how fast the brain thinks. compressing and decompressing files takes allot of brain power. so like if you want to open a zip file, the faster brain your PC has, the faster you can use the files that are compressed in the zip folder. also rendering images takes cpu power. (if it is not GPU accelerated) general tasks as opening files and loading maps in a games will also be faster with more mhz on the CPU. almost EVERY thing will be faster.
