Multi-tasking takes power, but not necessarily hoards of memory. What you are dong in Firefox isn't the memory hog you think it is. Working on large hi-res pictures in PhotoShop with many layers is a memory hog.
If you suspect that you are in need of better PageFile sizes, change them. Be aware that there is no performance benefit to having the PageFile on a different partition in the same physical drive as Windows. There is marked improvements if it is located on a different physical drive than Windows.
Try this, just to see if you like it...
No PageFile on System Drive.
Windows PageFile, Drive E׃ Custom size, Initial Size= 512MB, Maximum Size=4096MB
No Dump File, (Unless you actually think you'll use it in a crash). This will have No effect on system performance.