Jet,
It seems like Yamaha hasn't made mobile electronics amplifiers in a very long time. We used to carry them. With the harsher marine environment and if the Concord and Yamaha amplifiers are getting a little milage on them, they might not last for too many more seasons. So I wouldn't put alot of energy into the asthetic issue since things may change faster than you would like them to. However, I would give alot of consideration to the layout of the amplifers and the wiring so that I could facilitate a new amplifier(s) footprint with possibly connections coming from a different side or sides. Hopefully you can arrange things so that you don't have to make wholesale modifications to the amp board in adjusting to a change of a major component.
If your future amplifiers are JL Audio Class D models for example then the silver XDs will match, the footprint will be smaller and all connections will be on a single side. In XDs they currently have 1x300, 1x600, 2x100, 4x100, 1x300+2x100, 6x100, 1x300+4x100 plus several larger models to follow soon. And, the JX silver matches up very well with the previous E, A, and G series. In any case as technology improves amplifiers in general are becoming smaller for more power.

David
Earmark Marine