i want to be able to upgrade the gpu and storage so i5 7400?
i5 is a better gaming CPU, just depends on how much you're looking to spend.
not really going to be gaming a whole lot just work and multitasking
What multitasking exactly? Rendering a video, with 60 tabs open in Chrome and 4K content playing on your second monitor?
lots of tabs open and watching 4k/1080p videos on youtube
Frankly I expect you'd be fine with a Pentium or Core i3, that's still what I'd consider "light desktop usage". A faster chip couldn't hurt, but you may not be able to tell a difference between a $70 Pentium G4560 and $350 i7 7700K with your uses.