I know that you really need to upgrade your rig right away, but if you really like to put an E8400 on 780i chipset, I suggest grab the E8400 as soon as it becomes available cause Intel will launch their new CPUs with affordable price, and get 780i later and forget about the deal.
They slice the price of 680 series cause the 780i is just around the corner, just wait for a couple of months until the price of 780i drop a bit, it's worth of wait. If you uprading now and grab the deal, you just waste your bucks.
Trust me!! you're not alone who dyin' to feel the awesome power of 45nm and 780i. Just be a patience a bit my friend and don't bother your mind with marketing gimmicks, at the end, we all have a big smile for our long waiting technology!