Very Creative!
I know if it was mine, I would apply black paint to inverted machined grooves on the bottom of the amp.
That way the amp ties in with the black you have on your speakers, and the aluminum finish on your tweeters.
Another alternative, buy some 1/32" black pinstripe tape and wrap it, then your good to go. IMO, I think it will make the amp's appearance, feel more high end. Not sure what the tolerances on the inverted grooves you machined out are? I'm just guessing perhaps 1/32" would fit?