Actually the core of what we use is vbulletin, we've just done a bunch of custom mods to it. Upgrading would add new features, not really new performance.

Our DB is quite large, thats part of the problem. we could clean it up but the resulting tears from the change in post counts would make katrina seem like a summer shower.

The 2 servers we run on are reasonable, but a few years old. They arent $500 servers, one of them is a DL380G5, the other is just a custom built 1U. The DB box was pretty expensive. we could probably replace them both with a single box.

that wouldnt solve the problem exactly. the problem is the amount of posts/threads we have and how things are laid out. We'd need to make a few architecture changes, possibly move to 2 DB's etc etc. Going up from here is not cheap.

So right now, search goes off when we have problems.