limiting connections from tomcat to IIS - proxy? iptables?

I've webapp on tomcat6 which is connecting to an M$ PlayReady DRM instance on IIS6.0 The performance is seen to be best when we bench mark (using ab) the DRM service with 25 concurrent connections, which gives about 250 requests per second, which is ace. higher concurrent connections results in TCP/IP timeouts and other lower level mess. But there is no way to control how the tomcat app connects to the service - it's not internally managing a pool of connections etc, they are all isolated http connections to the server. Ideally I'd like a situation where we can have 25 http 1.1 connections being kept alive permanently from tomcat and requesting the licenses through this static pool of connections, which I think would the best performance. But this is not in the code, so was looking for a way to possibly simulate this at the Linux level. I was possibly thinking that iptables connlimit might be able to gracefully handle these connections, but whilst it could limit, it'd probably still annoy the app. What about a proxy? nginx (or possibly squid) seems potentially appealing to run on the tomcat server and hit on localhost as we might want to add additional DRM servers to use under load balance anyway. Could this take 100 incoming connections from tomcat, accept them all and proxy over the the IIS server in a more respectful manner? Any other angles?

EDIT - looking over mod_proxy for apache, which we are already using for conventional use on an apache instance in front of this tomcat instance, might be ideal. I can set a max value on the proxy_pass to only allow 25 connections, and keep them alive permanently. Is that my answer?

Many thanks,

Chris