Buying the latest and greatest will help in your quest but as time goes by it will lose that edge. Further, if you multi-task often then really you're placing the system at an disadvantage even though capable, sooner or later it will reach a tipping point of no return. After all, you can only do so much and wait the results in order to apply them. I wish it was better in answering this but find users want way too much from their systems, even if they paid for such. The results return of multi-tasking gets in the way of each task if overdone so a balance must be applied.
Of course if the new system is better than your current you should see improvement. All this balances out when actually applied to the real world. In other words, expect improvements but not that much. Like all new systems, the user will find out that it too will become slow. The adage, "what Intel giveth, MS taketh away" will apply.
Right now I have a Q6600 2.4GHz system w/3GB of RAM. After a couple years this is starting to run very slow and become unresponsive when doing basic things like browsing the web. I can either reformat and reinstall windows, which usually gives a pretty big performance boost or just buy a new system. I was thinking about an i7-970 w/9GB RAM. Technically this is a pretty significant upgrade, but will I notice a big different for what I'm using it for? I don't do any video encoding, or play games. The main thing I want to see an improvement with is when using multiple programs. I want to be able to do many things at once without a noticeable slowdown. I want to be able to switch between open programs and launch new ones very quickly too. Is this new machine going to be a lot more snappier in regards to running multiple programs, or will I not see much of an improvement there? It's a pretty expensive system, but would be worth it if I'm going to see a significantly faster/more responsive system, but I just want to make sure I'm not wasting my $$ on something that's not going to be drastically different than what I have now. Any suggestions?