Currently the relation between Opportunity and Quote / Order is set to System and Assign is set to Cascade All, resulting in a change of Owner of Quote and Order if the Opportunity is assigned. In our business the Quotes and Orders are not owned by the same user as the Opportunity.

Example: when a large chemical plant is built the owner of the plant requests numerous contractors to bid for building the plant. Each contractor requests our company to bid to them, but only one can win. Hence for reporting purposes there is one Opportunity representing the plant owner's demand and the Quotes represent the contractors' requests to bid. Since plant and contractors are rarely in the same sales region, different sales representatives are responsible for the Quotes and Opportunities.