Beautiful top!
Re quilting, I don't know if you like a lot of FMQ or not but I do and I think if done well, it won't detract from the design but add to it. I definitely wouldn't do an all-over as that would seriously detract from your lovely piecing and colour placement. I would do a curvaceous filler in the circular sections and a more angular filler in the other spaces. Check out Day Style Designs for pattern ideas or doodle until you come up with something. Perhaps a pebble with a swirl inside for the circles and a kind of squared off paisley elsewhere? This would subtly emphasise the difference between the circles and squares and would add lots of delicious background texture. :-D