Don't know about the 47xx, but I've got a 4960HQ in my current road-warrior laptop and its bloody awesome, I struggle to make it sweat despite running multiple VMWare instances and various copies of Adobe's finest ... right now its sitting 80% idle !
P.S. What are you doing to your current i7 that's causing you problems ? For your average home punter, any half-decent i7 should see you through to a 5 year lifecycle.... are you sure its the CPU and not something else that's slowing you down ?
P.S.P.S. I see you said
"Routinely I am working with large graphics - both hi-res bitmaps and vectors, and large, sometimes very large, text-based documents" .... if you're using current versions of Adobe Creative Cloud and a supported GPU, you shouldn't really see much processor impact from Adobe graphics processing because they've put a lot of work into farming all that out to the GPU rather than using the CPU like they used to.
As for large text documents, what software are you using ? Have you tried alternative software ? If may just be very poorly coded text editing software with poor memory management routines... certainly stuff like Adobe Indesign can cope with large documents with aplomb. Microsoft Office on the other hand is just shocking when it comes to large document memory management ....