The only thing you need to match is the bolt to the barrel pattern. The carrier is interchangeable. I'm not sure what pattern the Mega/Maten barrel is.
For optics I went with a Primary Arms 4-14 with ACSS reticle, with Warne QD rings. I haven't torture tested it, but I'm super happy with it especially for the price.
I have a Matrix set as well, and I love it.
Nice build, I'd hate to carry it!