Thing is, this is GDDR5 we're talking about here, which in terms of bandwidth I believe beats the pants off of the DDR3 memory that most people will be buying for new builds. Afaik GDDR5 memory can only be found on mid to high end graphics cards and the most powerful ones out there only have 6gb GDDR5 of memory (and cost over £800).
So the issue you have is that, even if you buy a £800 graphics card and 16gb of DDR3 memory, you'll be 2gb short of fast ram and still have system overheads to deal with. I get the feeling the next gen will encourage some very cool leaps in the PC market in terms of hardware.
Like i said in my last sentence not making any comparisons to the ps4, but it was more aimed at the fact you have nowhere near 8GB in your own system.
RAM is so cheap that most people who are building a custom pc usually go for 8GB "minimum" these days.
Also I do not think the RAM will be used to it's full capacity, in terms of specs, i reckon the CPU is the weakest part of the PS4, again it is more focused on number of cores rather than clock speed. they learnt their lesson that the cell was just far too difficult to program for because of it's complexity and number of cores and have gone for established tech this time round.
RAM > GPU > CPU
that's how i see the spec list for the ps4, the cpu imo is the weakest link and the RAM by far the strongest, the RAM is pioneering in terms of tech, not even top of the range pc's have that type of RAM as you say.
sure 2 of the cores may be used for the "system" one for background downloads and one for the OS most likely. that still leaves 6 cores free on the cpu for gaming. i don't think many games will utilise 6 cores that well, therefore it probably would have been better to go for a 6 core cpu with higher clock speeds, than an 8 core cpu with a low clock speed. even in 5 years time, i do not think any games will be able to utilise all those cores to capacity.
don't know much about the GPU, but people think it is weak, this has always been the case with any console released in terms of comparing it to pc hardware, therefore imo i do not think there is anything wrong with it as past GPU's have held up quite well, even though they were weak when compared to top end graphics card in the year of release.
i await to see the next microsoft's consoles specs to see how they match up to the ps4's. i hope they do not try and copy them but take their own programmers advice for future proofing the system.