OK. Firstly, you just assumed your computer was out of date, and that it was incapable of running the newest software. Or is this something you researched? If you had, I am sure that you would have uncovered that it is not the hardware (at least not all of it) that is slowing you down, but more likely an OS issue, a configuration / fragmentation issue or just one piece of hardware. These aren't opinions, they are facts and all sites will more or less agree on priorities when upgrading your system to play hardcore games.
If you have spent a ton of time searching fruitlessly on Google, perhaps you could let other people know which search terms you used and ask for help with that, or at least stop your potential advisors repeating your searches. This way, you can learn how to find the answers so you won't have to ask next time.
Secondly, you asked what the difference was between these two CPU's. It took me around 15 seconds to find the Wikipedia page (http://en.wikipedia.org/wiki/Pentium_D) after a simple Google search and that tells you what the differences between the 800 series and 900 series are.
The only set of opinions you asked for is gaming with MCE, which I take your comment about users on board - obviously some are biased and hold grudges. However, if you read a couple from different parts of the spectrum, you will get a fair and balanced view. And why should this forum be any different? Why would people who post elsewhere be invariably biased but the people who post here completely objective? Also, I very much doubt whether the sites themselves all have identical opinions - they would make each other extraneous and thus create openings in the market for sites with differing opinions.
Finally, would you post a question about a Formula 1 car on a forum that is frequented by mechanics who maintain family saloons? I doubt it, but this is the equivalent of that. Have you tried posting on a forum on a specialist gaming website? I am sure you will receive more accurate response there than you would here (you may even find someone who has posted the question before - did you ever think of that?).