Congrats with your new rig. You will not regret getting the i7.
When the new iMacs were announced I started to follow the discussions in this forum without registering as a user. Well, discussions... actually, in some cases it was interesting to learn more about some users' individual thought processes as I was in the same situation... looking at users like EugW. ;-)
This forum was very helpful for me, so thanks to everyone here!
I was on a Late 2008 MBP before, had upgraded RAM to 8 GB and replaced the HDD with a 1 TB Samsung Evo 840 SSD. Of course, this solution only worked for so long because for the most time I was using my work computer.
So when finally the latest iMac update was announced I knew I would get a new Mac. Actually, I had just been waiting for this update. I do photo and video editing, office work, some scientific and statistical analyses, run a virtual machine, play video and audio etc. Not the hardest tasks one can imagine but I wanted a computer that is really snappy. And who knows what will be in the future...
I had not expected this but actually the decisions in the buying process were really tough. Finally, I decided to get the 2 TB SSD. 1 TB would have been ok for now but I like to have a true all-in-one solution with no external devices (maybe except for an external drive for large video files) and in 1-2 years or even sooner I would need an external drive. For example, a portable 1 TB SSD would be a) not really inexpensive, b) significantly slower than PCIe flash, and c) not as elegant as a real AIO. So, this 2 TB SSD upgrade was really expensive but especially with APFS on the horizon I think it was worth it. I plan to use this iMac for at least 5-6 years and I just can't imagine I will be happy with a HDD in such a computer over all these years. Additionally, if I should sell the Mac one day, a large SSD (>512 GB) will be what people want. I should mention that I am a researcher at a university so I get an educational discount. However, I have to admit that this upgrade was pretty expensive.
With my decision for the 2 TB SSD, the high-end model with i5 7600K and Radeon Pro 580 was the only option. I decided to upgrade to the i7 7700K. Not because I think I really need it at the moment but I just don't want to regret choosing the i5 one day. Currently, I mostly shoot JPG and 1080p... yet, I will be shooting and editing more and more RAW and 4K in the future. I also think that, in the next years, software will make better use of more cores/threads. I have followed the heat/fan noise discussion very closely. However, in the end, I decided to go for the i7. I don't expect fan noise during normal use... and in those moments when I need max performance the fans will spin for a reason... I can live with that and appreciate the speed. My only other option would have been the i5 7600K which also might not be a completely cool and silent solution while not being much faster than the 7600. So I decided to go for the i7 which definitely has a higher performance, single-core and multi-core.
I went with the standard 8 GB RAM configuration and additionally got a Micron Crucial 32 GB kit (2x16) from Amazon Germany for under 210€. Not the 'for Mac' version but this should be fine considering the positive reports in this forum.
The iMac has arrived on Friday but I didn't have time to set it up. Will give you an update when I had the chance to play with it a little bit. Just wanted to say thank you for your opinions and also wanted to share my thoughts. ;-)