Joomla Site Optimisation

We are in desperate need of a Joomla Expert. We have a joomla site that that crashes the database when we have more than about 100 users on the site. We have a Dual Xeon server with 3GB of Ram. I need someone to go through our site and try optimise it and reduce the SQL queries. Currently over 160 queries on our homepage. I can provide more details and link on request. There may also be some work creating components to replace the current problem component installed on our site. Any questions please ask.