Well the only thing I would first correct on was the 'Cores' argument. More physical cores is good but when you go above 3 or 4, the problem is (and reason why AMD falls behind Intel with HALF as many 'cores') how the Cores get in each other way. Think of it this way, if you lifted a set of bricks from one place to another your a Single Core PC. Adding another worker (Dual Core) you can do twice the work and speed up the process. If you add more workers (TriCore, QuadCore), and step back you will tend to notice some workers (cores) are waiting for the other workers to get 'out of the way' so they can 'grab a brick' (grab data from memory) or 'drop a brick' (pass the processed data to the component -Sound, GPU, etc.- to 'do' what the data needs to do) and turn around to go back and get another. This is called THREADING, or how the Cores request data, then pass data; there is a quick point where you will see one core or more doing more work then the other cores, and basically get 'in the way'.
AMD decided 'more cores good' concept, Intel decided 'better threading good' concept with Hyperthreading. What results is (for normal using PC applications and for gaming - the 95% use of PCs) less core Intel processors outperform AMD systems with TWICE the number of physical cores. So while the FX-8xxx has 8 Cores, a i7 with 4 Cores but 4 HyperThread virtual cores performance TWICE the amount of performance then a FX-8xxx (and why every GPU benchmark you see tests with i7 not FX-8 and why every benchmark test ALWAYS has the i7s at the top).
If we drop down to a i5 (as your comparing), then you would think much 'less' performance out of the i5 then the FX-8, BUT what has happened until Haswell (i5-4xxx) is they were Either / OR (either i5 or FX-8) as 'about' the same performance. NOW with the Haswell line, it is i3 VS FX-8 then i5 then i7 repeatedly in the current benchmarks. AMD has decided (2013-2014) NOT to persue competing against Haswell and has completely shifted focus to the 90% other marketspace of the 'common user' needing a "low power, low COST, LOW DEMAND" answer, which they now push the APU line to address. As the FX -8xxx is the only real 'competition' to the low-medium level Intel line, AND any new AMD processor will use a new motherboard / CPU design (see the APUs) which will be INCOMPATIBLE with the FX-xxxx line requiring a Mobo AND CPU replacement, the FX-8xxx does not seem the best solution anymore as it is a 'dead end' when you think about both things.
That said, I would like to correct your thought process about worrying on the CPU for " video editing (Videostudio Pro X6 atm, probably the adobe suite later on) ". The CPU will not be the MOST important thing you should be considering. While yes a i5 can do video editing, by Intel's own admission a i7 is much better suited for it (more CPU / Thread cores better processing / coding of video). The real issues come from amount of RAM and buying a 'Gaming GPU' than a Workstation GPU. These are MUCH different. 8GB of RAM (common PC) is nothing in Video Editing, and 16GB is the "bare minimum", while commonly 32GB is used with many Amatuer - Pros going with 64GB to as high end as 256GB systems on specialized motherboards to handle those RAM needs.
In Video Editing it renders / encodes along with Audio editing / encoding into the outputted file / stream is completely opposite to a Video Game 'Rendering' to a screen for Frames Per Second performance. Video Editing / Rendering takes time, and a Gamer's GPU (the common consumer cards you see) are not designed to do those tasks, but Workstation GPUs like the Quadro (search Tom's Hardware Forum for Workstation and you will see many threads showing you typical and PRO setups) to do the rendering and encoding cuts the time to minutes and a couple hours then for Gaming GPU which can actually take days to render a Video. Conversely while a Workstation GPU is powerful it isn't built for FPS performance, and commonly (see again the forum threads) will performs almost half as well as a equal Gamer's GPU in gaming (say 90FPS in BF4 on a Titan, a Quadro would do 45 for rough example). So you really need to quantify your expectations and decide which is a priority, Video Editing or Gaming, then buy appropriately - is Frames Per Second more important then the HOURS / DAYS to Encode/Render a 20 minute Video?
If your looking for build suggestions numerous Workstation threads are on here with common builds, but the normal price range for Gamer's Desktops is around $1000 or more (typically a i7, 8GB, SSD, 1TB, etc.) but Video Editors START at $2500 upwards (typically either i7s or XEONs, 32GB, 512GB SSD, 4TB, etc.).