photoshop and ram performance question

[brass]

Hello, this is my first time on these forums so hopefully I'm posting this in the correct place. I'm having trouble figuring out if more memory will be beneficial to my pc in regards to photoshop. I'm using a 2.7ghz dualcore processor and 4gb of ddr2 ram on win7 64bit and often run photoshop cs5, illustrator and bridge all at the same time (switching back and forth) to edit files with sizes of around 100mb's each with multiple layers. I usually have my browser open with a fair amount of tabs open. Somewhere I read to click the bottom of the image and choose 'efficiency' and to watch that figure, that if it drops below 95% fairly often memory might be my issue. I'm not sure how often that number updates - upon first loading photoshop and opening an image the 'efficiency' read 33%. Not very good. But once I began selecting various layers, the efficiency moved up to 100%.

I've searched all over for recommendations and usually run into either people who feel the more the better no matter what or those giving advice for gaming. This seemed like a good place to get more detailed advice from seasoned people familiar with multitasking regarding ps/illustrator specifically and real world use (not just benchmarks). My system just seems sluggish with both of these applications open and I work with it quite a bit (6-8hrs a day). I just don't want to waste my time or money upgrading my memory if it won't offer a significant improvement. Any advice is welcome; Thanks in advance.

[Steve]

PS 64 bit is able to access as much memory as your computer will hold.
PS 32 bit will access just over 3gb. with a 64bit OS.

You're not getting much of the benefits of a 64 bit system.

Check this out:

Optimize performance | Photoshop CS4, CS5

[brass]

Thank you Steve. That's one of the links I've looked at. I've switched from ps32 to ps64 and haven't noticed any real performance differences even though my pc and everything is 64bit capable. As much as I've tried, can't find any recommendations for how much ram is used with both ps and illustrator open. I'm guessing this isn't completely unusual, to be working in both applications. There's a place to adjust how much ram is available to ps, but i couldn't find a setting like that or an 'efficiency' tab for illustrator to compare performance to. It also seems like a large program, but I've read that editing vector images in .ai files is less memory hungry by nature so I'm having a hard time telling if ram is my bottleneck. Ram use under performance monitor in windows doesn't seem to indicate much use over 3.2gb, but that may just be preserving some for the system and instead hitting the swap file causing the sluggishness. If 4gb's of ddr2 ram is enough then I'll have to try and find another option like maybe an SSD drive. My other option was to move to 8gb's of ddr3. I'm a little low on funds at the moment or else I'd just upgrade my ddr2 to 8gb's, but it's sadly more cost effective (cheaper) to move to a different motherboard and ddr3.