The absolute cheapest tickets I have ever seen are through Connections. Check Mousesavers.com for detailed info on the Connections program. Typically there is an annual fee involved in using Connections, but they have a 30-day trial period for only $1. Connections does have it's own set of associated headaches, which is why I've never tried it myself. But it may be worth a look if you're shooting for rock-bottom prices.
I've used Florida Orlando Tickets myself, and find them to be reliable. A handful of other brokers have been mentioned on these boards, too, who have similar prices.
I find it hard to believe that the cheapest tickets you can find are direct through Disney. In my past comparisons, including all of Disney's official discounting programs, I've never had them be the best deal for what I needed. Someone mentioned that tax may not be included in the prices you quoted, and I suspect that is true.
AAA may be a good option, but not necessarily in all areas (or to non-members). A few months ago I called my local office and was told that they only sell discounted tickets as part of their complete vacation packages. It had to be at least a room / ticket package to get a discount from AAA.
Regarding your question on the Disney Club discount, they no longer offer a discount on the 4-day park hoppers you want. I believe the DC discounts start with the 5-day PH Plus.