I play lower limits (25,50,100) but heres what i would do.

Hes either on a draw or has you beat. If you check here, you will either give him a free draw or anouce to him that your weak.

I always make the smallest bet here that I think will let him know I have somthing, perhaps am trying to keep him in. People will seldom call two bets in a row, then lead out on a bluff on a river.

I would bet half the pot, and hope to check behind the river. If he bets out on the river I lay it down. This works for me at lower limits.

On a side note. I wouldnt play K9s or raise with it. Just my preference.