Use GigE cards on the servers with a jumbo MTU and only buy IP network access from a service provider who supports jumbo MTUs end-to-end through their network.
I'm not sure that I see how jumbo frames help (very much). The principal issue here is ...
The people who know what helps are the ones who have been setting the Internet land speed records. They typically use frames larger than 1500. As for the principal issue, well, if there are several factors that will contribute to solving the problem, I think that you get better results if you attack all of them in parallel. Then, if you learn that there really is one principal factor and you need some management approval to move on that issue, you will have laid the groundwork for making a business case because you've already done all the other things. --Michael Dillon