9800 GTX SLI draws ~228W or ~19A by themselves. The Silencer 610 has 49A that would leave you 30A for the rest of the system but you will need Molex to PCIe power adapters, which often come with the cards. A cheap PSU of the same spec will not work. The silencer 750 would leave you more headroom and the prices are extremely cheap right now.
You are about to answer a thread that has been inactive for more than 6 months. If you still wish to proceed, please ensure that your posting is original and does not duplicate or overlap any prior responses to this thread.