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My favorite tool to test throughput is called Jperf 2.0 from here:
http://sourceforge.net/projects/iperf (the program is called Jperf)

It's simple. Unzip it, you'll see a folder called Jperf 2.0...

Based on the very limited amount of information you provided, the 5412zl model seems a plausible solution for your LAN. But, I'd make sure that throughput is the culprit before you fork out that kind...