Control sound system using iMac

Hello,

I would like to accomplish the following:

1. Control a sound system (speakers) using my iMac.
2. I would like to broadcast music to several speakers through my house.
3. I would like to listen the same music that I broadcast in my iMac or if I prefer, I would like to listen to something different of what I am broadcasting in my iMac or nothing at all.
4. I would like to set up an alarm that plays different sounds at different times throughout the day, and I'd like those to be listened in all the speakers throughout the house and interrupt the music if it's playing.
5. I do not want the 'normal' computer sounds to be broadcasted to the speakers, like when I send an email, or I send a tweet, etc.
6. I would like to be able to change the music that is playing from my iPad or iPhone.

Is there a way to accomplish this? or it's too complicated?

Now I own an iPad, iPhone and iMac, but I have no speakers yet.

Thanks in advance for your input!

crstnmx