As it is, you can get cheap 8 core CPUs but it still begs the question why. If you're not making use of the extra cores then it's generally better to put your money elsewhere. Well, Vishera closed the gap a lot (whereas Zambezi actually made it worse in a lot of cases) and as of writing the FX-8320 is about the same price as the i5-3550P and the FX-8350 can be had for $200. Thing is again, if you're not making use of the extra cores then there's not much argument for them.
This is a "single threaded" task:
[Image: http://media.bestofmicro.com/Y/5/357629/original/lame.png]
This is a "multi-threaded" task:
[Image: http://media.bestofmicro.com/X/Q/357614/original/abbyy%20finereader.png]
For tasks that use fewer threads, the i5's will tend to beat the AMD octocores because they're "better". However if there are tasks that let the octocore fully utilise all eight cores then the octocore will perform around better than the i5 quad cores. The i7 quadcores are a bit different due to hyperthreading, sometimes the 8 core visheras come really close to the i7-3770k, sometimes the i7-3770k still destroys the 8 core vishera.
A lot of tasks your computer performs will fall in between these extreme examples, not single-threaded nor not vastly multi-threaded. Gaming whilst improving continues to make poor use of lots of cores, even quad cores can represent significant diminishing returns over dual cores.
To sum it all up, the most important question to ask yourself is what you'll be using the computer for and how much you want to spend on various parts. If you have to buy prebuilt, give links to sellers you can buy from (I said this before but you seem to have not seen it).