No, I would not cut the fabric up. I love the way you have put the fabrics together and I think that it works very well. I have read everyone's post and there has been so much mention of a cream border which I think is quite nice but considering the combination you have, would stand out quite a lot especially if it is a thick border. A black border will more or less blend into the quilt as there is a fair amount of black in there already but could make it a little dark. A combination of both would be interesting. I think that it is really your preference as to what sort of effect you want. I will be looking out for your finished quilt to see what you have decided to do. Thank you for the opportunity to offer you my thoughts on this already lovely combination of fabrics.
P.S. Looking at your arrangement again, you could choose to split the red and black stripe fabric and insert a thin cream strip between them and join the 2 flowered strips to either side. That way if you choose to use a cream border that could help balance it a little perhaps? Just a thought. Best wishes.