Explanation
The IS auditor's primary concern when auditing the proposed acquisition of new computer hardware is that a clear business case has been established. A business case is a document that justifies the need, feasibility, and benefits of a proposed project or investment. A clear business case can help to ensure that the acquisition of new computer hardware is aligned with the organization's goals, objectives, and requirements, and that it provides value for money and return on investment. The other options are not as important as establishing a clear business case, as they do not address the rationale or justification for acquiring new computer hardware.
References: CISA Review Manual, 27th Edition, page 467