It gives me a headache too sometimes ;)
With the Universal Studios ticket, a regular 1 day pass is $80. There is the $15 off the discount I listed, so that would be $65.
If your going to purchase a Disneyland ticket by itself, you should just purchase the 4 day Parkhopper promotional ticket online, since they are only offered online.
I believe you can upgrade a promtional ticket at Disneyland. I think its likely you can, but, you would have to pay the difference between what you paid for a 3 day promotional Parkhopper ( $220) and the cost of a regular 4 day Parkhopper at Disneyland which is $275 right now so $55. As you cant purchase the 4 day promotional tickets at Disneyland, only online.
Since you are not planning on visiting Sea World, and, you have the advantage of the Disneyland promotional discount tickets, its basically a "wash" with both ideas..
1----Purchase the SoCal city Pass through costco Canada, $279, add a day to your 3 day Parkhopper within the pass...$25, so $304 total for adults for the upgraded 4 day Parkhopper/SoCal city Pass combo.
2----Purchase a 4 promotional discount day Parkhopper ticket online... $245, 1 day Universal Studios ticket with discount, $65 so $310 per adult for a 4 day Parkhopper and 1 day Universal Studios ticket.
However, its $5 less to use the SoCal City pass with the SeaWorld ticket included in option #1, so it maybe something you want to consider when your visiting San Diego.
Edited: 8:06 pm, January 20, 2013