The answer to this is that the question is too complicated to answer, a lot depends upon implementation. The base requirements are low (you couldn't but a new machine this poorly spec'd now:
http://en.csharp-online.net/WCF_Services%E2%80%94Hardware_Requirements[
^]
The service doesn't sound too heavy. The searching should be performed on the SQL server, so the WCF service is "idle" while this is happening. I'd host the website and database on a separate machines.
The only thing you can do is stress test the services to see how they perform, in general I'd say a poor response time indicates a poor design.