Hey there,
I may be able to shed a bit more light on this for you all, until something can be done about it. Basically, the reason why the site is getting slow, is simply due to the number of visitors that are on the site at one time, and how many simultaneous mySQL database connections can be maintained on one server, with high loads.
Translated into English: there are simply too many people on the forums at times, and the one server just can't keep up. It has nothing to do with the search feature of the forums. It's just simply too overloaded with visitors.
The simple answer is that yes another server is needed to aleviate these loads. The problem will be coming up with the money to buy/build one, and the time to deploy it. I actually do this sort of work for a living, and have had a look at the loads on the server at various times of the day, and then reporting my thoughts to Spark. It's simply a matter of a very busy server being overwhelmed.
It bascially comes down to simple time and money. We're all pretty busy people, and Spark is also trying to run a business as well. I've offered my services to him in regards to building him another server, but he has a few venues to consider before making his choices as well. When it comes to servers for applications like this, you need to make smart, informed decisions, or it could end up costing you more in the end.
Just be patient guys, I can personally assure you that he's most assuredly working on the solution for this.
I also wanted to express my thanks to him, and the the other founding members, for making such a great resource available. It would be quite the hole to fill if it were gone.