To get a little better image quality you pay a premium. Where you pay a few hundred bucks for a cheaper kit lens you might pay in the thousands for the upgrade to a canon L lens. You might pay 3 times as much but the improvement will be fractional, definitely not 3x better. If you are happy with the quality your present lenses put out, why care what others think is better. You found what works for you.

The one lens that I would point you toward, because flowers, image quality and color seem to be a reoccurring theme is the canon 100mm L IS macro lens. It will do several of the things you mentioned very well and is an extremely sharp lens. It would be an excellent lens as your first L lens and a start to expanding your kit.