There is going to be good value in the middle rounds for CB's. A few of my favorite mid-round corners are;
U of Conneticut (CB) Blidi Wreh-Wilson - He has good size, 6-2 190 lbs and he has a lot of experience playing press man coverage. It too early to really tell what round he may go, but I'm guessing somewhere between the 2nd - 4th rounds.
U of Connecticut (CB) Dwayne Gratz - Gratz plays oppostie of Wreh-Wilson and is also a mid-round prospect. Gratz has good size, 6-0 198 lbs and he also has a lot of experience playing man-press coverage. Gratz would be a good fit as the nickle CB for the Seahawks. He has enough size that the coaching staff likes in CB's and yet he still has quick feet to press then turn and run with a slot WR. I'm guessing he will be drafted somewhere between the 3rd - 5th rounds.
Tulsa (CB) Lowell Rose - Rose has nice size, 6-0 192 lbs, and I believe he plays a little bit of press-man.
A mid-late round FS/SS that has Seahawk size is Tulsa FS Dexter McCoil. McCoil is 6-4 222 lbs and is a ball-hawk. He has 17 career interceptions, but he is a bit of a finesse player considering his size.