With your explanation, which is very useful, I just can't see the Haswell "choking." It will plough through your files like a hot knife through butter, especially with an adequate video card.
If you had said your budget was unlimited and money wasn't an issue, then sure, get the six-core for the small advantages it may offer in your current operations and possible future operations you have yet to detail. But I do think the Haswell/32gb/770 combination will perform better overall for the operations you detail, but sure.. it's easier to add a video card to boost performance but maybe not cheaper depending on the card. Do you buy a $350 770 of a $500 790 a $750 Quadro 4000 or a $1800 Quadro 5000.. just to be sure.
And there is always the 8 core Xeons, duals if dare..
What we're really talking about is where the point of marginal returns are related to cost of a machine designed to process still files related to speed..
You know, it might be educational for all of us if you created an action for Photoshop CC and put up a file.. and let us run that action for you. Get some hard numbers on exactly how much time we're talking about? Then you could make an informed decision based on fact and recommendation. It might help others out too.
Back to your SSD's. This is another area where steep gains can be made.. But one which that pesky point of marginal returns cautions. Conventional use for imaging is to use a 256gb fast SSD w/TRIM for your system drive where the 256gb number leaves at least half the disk free to designate for caches. And then another, perhaps slower more economical SSD as a work drive for current files. I do this myself with a Synology 1813+ hooked up to my LAN ports for archiving at 120-140mbps. One could go further: If a Lightroom user a dedicated cache/preview SSD speeds things up. Some don't mind the cost of putting two SSD's in a RAID 0..
One more consideration while we skim this topic: Heat Kills. Noise Deafens. Manufacturers always knew this but because design all too often butted heads with performance they didn't talk a lot about it I don't particularly like Apple's new Pro design, but it really makes sense from the heat and noise perspective. Taking all but two SSD's out of case means either a TB or LAN array depending on need. Haswells are very cool CPU's even when compared to Ivy'. By keeping the mechanical hard drives out of the case, or even limiting it just one, you can easily run a sub-30c machine at idle and sub-50c loaded. With a well designed case (I prefer Lian-li) and cooler you can have all that with very little noise. In fact some would say it's silent depending on how good their ears are.
We live in good times with even better choices in technology.