From what I hear...sound bar is simple. Grind away the plastic along the edges until your speaker fits properly. What I'd probably do is find the cutout diameter for those particular speakers (should be listed in the specs either on the box or online), make a pattern, trace it, and trim it out to fit that pattern. Then you just need to drill holes for the mounting screws (make sure they're a little smaller than the actual screws or they won't thread into anything...and then just gently screw them into the new holes. Remember it's plastic so don't overtighten your screws or you may strip them. I'd just snug em up.
The front is a little more complicated, but not by much... you need an adapter plate for the front (not the rear though). You also have to cut out a piece of metal. The directions show exactly what will need cut out...and you'll see it once you've got the old speaker out and the adapter plate lined up where it needs to go. That's the only modification for the front that I'm aware of. The hardest part I hear is cutting through the metal...it looks thin, but apparently it's a little tougher to cut through than you would expect. So if you use a dremel...might pick up a few extra grinding wheels. lol