Building a Cheap Desktop

So, my mom has increasingly grown frustrated working on small screens and with a trackpad, and when she occasionally works on my desktop, she is amazed on how much more productive she is. So, surprisingly, she gave me the go ahead on building her a cheap system for her.

She is makes homework packets for math classes and does heavy email work. So she doesn't need too much power at all. She does get frustrated when her computer doesn't work or is slow so I do not want to skimp too much on on processing power. She also likes to run extreme numbers of browser tabs.

My budget I think is 400$ or under.

My current system, is Mini-ITX with a MSI 85I motherboard and a low end haswell i3 with 4 gigs of ram. I am undecided right now about whether I should go 300GB hard drive or 60 GB SSD.

Do you guys have any idea about I could change and any good deals for storage?

UPDATE: I have gotten a bit more leeway in the price and so have bumped the ram and gotten a 120 GB SSD