In puget sound I like to use a rio outbound line with a clear intermediate head. When I'm fishing at Neah Bay or more of an open ocean situation I like the rio striper lines. They're integrated density compensated shooting heads with intermediate sink running lines. Those will also work in the puget sound from a boat, but not so much if you plan on doing any beach fishing.
If you are looking for a 300gr replacement, I think the AirFlo Depthfinder lines are hard to beat. I've had a couple T300s and these airflo lines are nicer to cast and seem to be more durable. I've got a 300, 400 and 500 of those that I use out at Neah for Coho and bottom fish. I also always have a dry line strung up for popper action or to feed the krill feeders. Sometimes I string up a 200gr line too... AirFlo Depthfinder.
The SA Streamer Express lines are very nice, too, and are very similar lines to the Outbound and Airflo lines noted above. I believe the Streamer Express lines were out a year or so before the others, but SA doesn't seem to do as a good of a job as Rio in marketing those 'specialty' lines.
For my 6/7, I use a Streamer Express (it has an intermediate running line with sinking head) when I'm trying to get some depth or the current is moving quickly. I also use a WF6 Airflo multi-tip line from the boat when fishing over the tops of kelp and when the current is a little slower and I may not want to get too deep. I also take along a 24' chunk of Cortland LC-13 (sinks at 8-9" per second), and loop it on to the Airflo running line when I want to get down fast and deep. The floating running line I'm sure slows down the descent of the LC-13, but it's pretty convenient to have that one running line with all of those factory heads and the LC-13. I've used that LC-13 to fish deep at Sekiu and Neah Bay during the day when the fish might be at the 25'+ depth.