I don't want to get too technical with you but if you want to get a core ix processor you will have to replace your motherboard. Different manufacturers use different connections on the processors (and even different generations by the same manufacturer are different).
The first thing I need to know is whether you are confident with building a computer; the problem with replacing the motherboard is that you have to take every single piece out and then put it all back together properly, it's not as easy as just replacing one component. It isn't the hardest thing in the world, it's just a matter of ensuring that everything is plugged in to the right spot correctly.
If you are confident with this I will find you a new MOBO and processor for under £300