What about SITD around the border, then tying in the center? It might be that you could use SITD along the edges of the block just to hold everything together securely, then tie in the centers of the blocks (and perhaps the block seams) to add visual interest. Even with all your super colors dancing around the top, the ties would certainly pop out, too! Whatever you decide, you will have a great quilt when you're finished with it.