I was looking round on scan and saw a quad core cpu, this one infact Computer hardware and software at amazing prices, available online from Scan Computers UK pretty cheap and so im wondering if itd be much better than my current, if price isnt a problem thanks
Depends on what you're doing or want to do. Right now, very few games take advantage of more than one core, let alone 4. Now, if you like gaming and video encoding at the same time, that would be a good investment. However, if you don't, you're going to find that you just drop a chunk of change for naught.
also would i notice much of a difference in performance if i stuck another 2gb of ram in my machine, bringing it to 4gb?
That's more related to the hard drive and amount of RAM, to a certain extent. If you're running XP or 32-bit Vista, it can work with up to 4GB, but the OS is incapable of making use of all of it, so you'll be stuck with either 512MB or a full 1GB that the OS is ignoring. That's kind of an issue with 32-bit in general: OSes and CPU architecture. 64-bit makes the gap, so if you have the 64-bit version of XP or Vista, then you'll get full use out of 4GB. If the memory is where a bottleneck is, then yeah, that'd be something to look into. It can help, but it depends on what app. You're probably not going to see improvements in your web browser so much as a newer game or large video or photo files.