Heavey load of 200 users and router board HEx

Dear Friends
i am using hex series router board on my small hometown isp . i am using them from last some months from last two months on friday night to sunday night it works very slow . although both of them were working smoothly one month ago.
I have Ubnt wireless equipment on clients side.
on my side using three hex router board for isolating users like better good and fair speed (based on price ).
now i am thinking about some cooperate level equipment on my site.
so please recommend me some good hardware in router board.

RB1100Dx4