Speaking from years of experience (both mine & others

), I can tell you right now to not even think about bookshelf speakers for your main 3 speakers.
Not that there is anything wrong with using 5 or 7 identical bookshelf speakers. They actually make perfect sense.
But in this hobby, you will develop "UPGRADITIS". You will keep on wanting something MORE & BIGGER.
So just go with something MORE & BIGGER right off the bat and just build up your system as you go along. Like you mentioned, you might go with a 2.0 system now. Save some money and go to 3.0, then 5.1, etc.
The most important thing about the speakers you buy is the RETURN policy.
If you don't like how they sound in your OWN room, can you return them for free?