Hello I want to buy a router between c6 and c60.

My flat is about 1700sq. ft. and the router position is in the corner room.

I can't move my router somewhere center in the flat.

So suggest me whether I should go for the c6 or c60 model?

My priorities are range/coverage and strength. I can't boost up my budget and go for the better one and got stuck between these two.

I have another router so if I buy c6 can I use it as a repeater wirelessly?

Please give a solution as soon as possible.
Thank you.