I think - stop trying to spend money when you dont need to!
I feel this is going to be a long post...
The only difference between the i5 and the i7 is Hyperthreading. However, there is no game out that's even optimised to use 3 cores fully, very few fully use 2, and most still linger around on 1. Take Diablo 3 for instance. Because of this there is absolutely no performance difference whatsoever in gaming between the i5 and the i7. Hell, in 99% of cases there's not even a difference between an i3 and an i7. The only time the extra cores/threads are used, is in video rendering, and other imaging software, which you are not using. It therefore will literally make no difference whatsoever if you buy the i5 or the i7, so save money and get the i5. If you have future proofing in mind - you're already future proofing in not getting the i3, and no games will use even 4 cores of your i5 for a long long time, by which you'll have upgraded the PC anyway.
Now the TIM...
There isnt really even an issue IMO. You can overclock to around 4.5/4.6ghz before temperatures start to rise to higher levels than on Sandybridge. However, in order to overclock to this level on both sandy and ivy - you'd be putting more volts through the chip than it can even handle for a 24/7 OC. Someone recently on these forums even was saying they had their 2700k running at 5ghz, and it was stable for 1 month before it started requiring more and more volts. This is degradation, and you never want to be putting so many volts through it that it causes degradation, and so you want to leave it at around the 4.5/4.6ghz mark anyway. At which point - Ivy is better anyway, so you may as well stay with Ivy.
The 2011 3820 will actually be worse - as it's a locked multiplier and so you wont be able to OC it to as high levels very easily at all - so forget that idea completely.
Now the RAM...
Windows is coded in 32 bit (regardless of whether you have 32 or 64 bit OS). This means the OS itself can only ever use maximum of 4gb of RAM. And I really mean maximum as the OS will very rarely go above 2gb. All software that you will be using - ie - games, are also coded in 32bit. So they can only use a maximum of 4gb. This means, your computer will only ever use a maximum of 8gb anyway, so it's a complete waste of money anyway. So no - it definitely is not worth the other 8gb.
As I've already said for the Soundcard, the Z77 board's soundcards are already good. You don't really need a soundcard anyway...but, you may decide you want one... You may as well go without and save the £130 on the soundcard, and use the onboard sound. If you dont think it's up to par, then you can buy the soundcard. It just seems pointless to me to buy it because you're expecting the onboard sound to have issues - when it most likely wont.
Hope this clears a few things up - and I think I'm gunna copy and paste this into a word document, as I've written the same old crap about the CPU and RAM usage so many times now, I may as well just copy and paste it in