First rig after a few years: Need some rebriefing

First of all: Hi there.

I am currently planning on a new PC build. Have done that times before, however it has been a while since I have stopped keeping track of all the hardware stuff. Consequently, my PC by now is hopelessly outdated. So, even if I have a basic knowledge of things, I would need some hints and some answers, though. Any help is highly appreciated.
This system will primarily be used for everyday things such as office, coding, photo editing and the like, but should have the power to run current gen games without problems. (and last for years to come, of course).

Let´s get started: Initial Budget: ~800€. (Yes, I´m european - Austria to be precise)
Parts in consideration left me with these cost ranges (note: as I did not decide anything specific yet, I am mostly not listing specific parts)

  • AMD option: (socket AM3+)
  • Mainboard AMD: ~75-125€
  • CPU: 130-200€ (go big or go home: 8core 8350 4GHz for 185€)
  • Intel option: (socket 1155) (Note I do not know about the different Intel codenames, platforms, etc.)
  • Mainboard Intel: ~75-125€ (I figured a Z77 is a good choice for a new system?)
  • Mainboard Intel mini-ITX: ~125-175€ (see case - again Z77)
  • CPU: 175-200€ (I prefer the 3570k in this case. I like to choose the CPU in the upper class before the price curve gets to steep, this one just happens to sit in the sweet spot)
    I figured, Intel or AMD is about the same cost. Add an additional 50-75€ for a mini-ITX system though.
  • GPU: Should be kept under 200€. Would a nvidia or an AMD give me the most power per coin? How about an 7770 (130€) or an 7870 (200€)? Would aequivalent nvidia cards be cheaper/more expensive? Advice is highly needed here.
  • CPU cooler: ~40-50€
  • RAM: 60€ for 8GB (Or double the amount and the cost - propably not neccessary)
  • Power Supply: ~75-150€ (from pretty basic to semi-passive, full modular and all that) 650W+ targeted. (So far I have never taken much thought about the PS - always used the cheapest one that fitted)
  • SSD: 200€ for 256GB (100€ for 128GB)
  • HDD: 2x 50€ for 2x 2TB (RAID-0)
  • Case: 75-100€  I really like the appearance of the BitFenix prodigy. (75€, only takes mini-ITX boards though) But as there are no current AMD boards in mini-ITX form factor, it´s only an option if I go with Intel. I have yet to find a slightly bigger case that I like just as much.*)

All things considered, I´ll barely hit my initial budget with the lower end for each part. As I do not want to save on the wrong end, what do you recommend should get more attention? (And let´s increase that budget to 1.000 - might get overrun as well [much like any budget I guess ;) ])

Additional questions:
* Do I need PCIe 3.0? There is only one board for the AMD platform with that - ASUS Sabertooth (it has 3!, seems a little overkill) - which is listed higher than I´d like to spend (180€). All the Intel boards have it though
* AFAIK a new Intel platform(?) is about to show up. Is it wise to buy the other one now? Or would it be to expensive to consider for now? Would the appearence of a new platform drive the cost of the current ones down?
* Are there any relevant mainboard features I should consider?

Thank you in advance. I am looking forward to some great insights :)
Cheers, Franz

*) I asked BitFenix support wheter an ATX version of the prodigy is in consideration, and they hinted on Computex in two weeks. Will be interesting if something emerges.