so the current build is sitting around $1200 and you want that to at least come down to $800 at best.
you are simply going to either up the budget or downgrade some components.
I realised I'm stating the obvious, but it's really that simple.
for example, liquid cooling, really, is that needed, I'm yet to see the supplied, standard heatsink and fan not do the job.
and an i7?, an article in my monthly PC mag a few issues ago had an excellent report on gaming rigs and compared Core i3, i5 and i7's and basically boiled it down to an i3 could cut the mustard for a budget gaming rig. i5 of course was better and i7 was just a waste of money with only a small percentage of performance improvement.
it will all come down to what areas you are willing to sacrifice for cost.