Weddingbee boards

I think the answer to this somewhat depends on how much work you want to put in beforehand. 

We did our own music and didn't rent anything.  We literally just plugged the laptop directly into the venue's soundsystem (it was a restaurant and the sound system wasn't anything special...really just a basic stereo type thing with speakers around the room) and the music was awesome.  That's not just my biased opinion :).  We had people commenting on how much they loved the music all night and when we told them, they didn't believe we did it ourselves.  I've listened to our playlists since the wedding and when I'm actually listening rather than partying, I'm completely blown away how good it sounds and the obvious work that went into it.

BUT my husband spent a friggin ridiculous amount of time preparing everything (I have no idea how much of that time was necessary and how much of it was because he's an obsessive perfectionist).  He used a computer program to go through all the music before hand to make sure it was all equalized so we wouldn't have to suddenly jump up and turn down (or up) the volume and also to make the transitions between the songs be smooth.  Whatever program he used was free.

I have no idea about advice on mixers, amplifiers, etc.  Just wanted to pipe in and say they aren't absolutely necessary...but you either need the equipment, or need to dedicate a lot of time beforehand...just depends which you'd rather do.  My husband enjoyed doing it and had the time (or used it to procrastinate on his grad work :-p), so for us that worked.  For most people, renting is probably easier :)...but if anyone wants to know what he did, message me and I'll get the details from him.