Speaker placement is essential in getting good sound. The first thing that is good is it sounds like you have music speakers which honestly work even better for home theater in my opinion, the key is getting the right placement.
First thing is no you don't want to spread them out farther, the key is if they are setup right for stereo then they will sound right for surround sound. Spend time getting them to sound right for music and you will be happy with the results when you play movies as well.
Position of speakers in the room will have a large effect on the overall frequency response, bass response, and soundstaging. All speakers will have different requirements when it comes to placement it is honestly trial and error. It takes time and patience to get it right but well worth the effort.
The key is you want quality of bass over quantity of bass, but with the right speaker position you will get both.
I generally like to start with the 1/3 rule, which is 1/3 from the back wall. This in most situations is not practical so the next best is 1/5th. Start with the speakers about 8ft apart. Play music with good bass detail, and play with the position from the back wall to get the best low bass extension and detail. When you get the placement right you should be able to hear all bass notes clearly and with authority. Distance from side walls and speaker distance apart will effect midrange, upper bass detail, and soundstaging. Again once the low bass is right, then you can play with the distance apart to get the rest of the sound quality's you desire.
Speaker placement is both Art & Science, use the rules I gave you and you should be able to get the desired results you personally prefer.
Kevin
40 years high end audio video specialist