Big button design

Alright, I am redesigning a multi-step process where the user adds new contacts to his/her address book.

In the first step, the user chooses between three possible addition methods: file import, crm connector or manual addition.

Now, I am debating how to design this screen. This is my first draft:

I like how the three huge buttons stand out and draw a lot of attention to the user.

However, compared to the side menu they look incredibly big (too big?).

My question is: How to design a screen like this where the user only has very few but important options?

Small buttons, radio boxes, drop downs, etc. look ridiculous - but is this the way to go?

Any feedback is valuable feedback - thanks.