[syslog-ng] Beginner's questions for deploying syslog-ng

Hi All, I'm planning create a centralized logging server for our network. We have 100 cisco routers and switches. Not too big organization. Suppose every cisco must have log to be sent to centralized logging server. I'm considering to deploy syslog-ng in CentOS 5. As I understand, I also need a web front end for user to search the log easily. Someone recommend splunk to do this front end job. I checked it out and found the free version of splunk has a 500MB/day for the indexing size. I'm not sure how this limit will affect on our network. Or is there any other good web front end for use with syslog-ng? Any help is appreciated. Lou