Well i think the results you are getting are aligned to what it should be, although i have never worked with arria gx or cyclone so i cant comment on the 1Gb/s you are saying for the outputs but i really doubt that arria gx or cyclone can give such a baud rate.
Anyways i am also attaching a snap shot from arria2 gx manual.
Might give you a better view of the max frequency operations.
Nevertheless even if your lc count is only 50 even then i think the results are reasonable .
If you provide some insight on the resource counts and your sdc some experts here might help you.
GOOD LUCK