The Logan 665 will cut 8 ply, you just have to go slow and make sure the blade is lightly scoring the support mat. It is what I use for museum shows and it looks great! I have an upcoming show at the museum of art in my home town and for this I use the 2 ply for mounting and the 8 ply for the mat.

Setting your work apart and mounting it and matting it professionally does not mean your work is weak.