Hello sknk,
The short answer to your question about the CM4228HD is yes for KING NBC and KIRO CBS and no for KCPQ 13. The CM4228HD is a UHF design. That works great for the majority of your channels. However KCTS 9, KSTW 11 and KCPQ 13 are all high-VHF signals. Especially in an attic situation, you need an antenna that is designed to receive these signals.
I'm sure you've read about attic installations on this forum. They aren't ideal and can be more hassle than they are worth. Especially in your situation you have 1 and 2 edge signal obstructions to your roof. Adding your roof to it, you have 2 and 3 edge obstructions.
With the attic also, be prepared for potentially unreliable reception. Antennas in attics are subject to household electronic interference and multipath issues due to the signals passing through solid matter.
That said, keep your CM4228. Orientate it in your attic to magnetic heading 227. Add a second antenna if you have the space, a
Antennacraft Y5-7-13.
http://www.solidsignal.com/pview.asp...u=716079000987. Orientate Y5-7-13 to magnetic heading 227 as well.
Order a signal combiner. The
Antennas Direct EU385CF is a quality performer.
http://www.solidsignal.com/pview.asp...u=853748001705. Input 4228 coax into UHF input, take Y5-7-13 coax and run it into the VHF input. Run single output coax down.
Preamps can be a mixed bag in attics. If the signal arriving at the antenna is bouncing around and drop outs occur because of it, a preamp won't fix it. Reliable reception is best when there is no obstructions between antenna and transmitter.
You didn't mention how many TVs you want to service.
Doing two antennas one dedicated to UHF and one to high-VHF will be your best chance within the attic for reliable reception of the majority of Seattle area signals.