I just ordered an E5200 from OutletPC for less than $80. It is a boxed CPU and the stepping is M0 so this should just be a drop-in replacement without the need of the BIOS upgrade. I will post again once I receive the CPU to confirm its spec.
http://www.outletpc.com/c1894.htmlI just received the CPU and it is brand new in a retail box. Unfortunately, the S-spec is SLB9T so it will not be a straight forward drop-in replacement. I do plan to perform the upgrade in November when the warranty on my EX485 expires.