In the patch you write: "topDocOrdered - Creates a TopDocCollector that requires in order docs" - did you mean TopScoreDocCollector? Because TopDocCollector is abstract ...
I think the following:
+ Class<? extends Collector> clazz = (Class<? extends Collector>) Class.forName(clnName);
+ collector = clazz.newInstance();
can be written as Class.forName(clnName).asSubclass(Collector.class).newInstance();
Also, and it's a style issue, can you remove the '== true/false' from ifs?
I'd change if (clnName.equals("") == false) to if (clnName.length() > 0).
Why does benchmark/build.xml now relies on the compiled classes/test (of core)?