[snip everything] In the first test, I noticed they were using intel etherexpress pro cards. I don't mean to start a verbal holy war, or say anything about the cards themselves, but I've heard from many people that the linux driver support for these cards is (much) less than optimal.
My recomendation for an excelent card at a decent price is something supported by the tulip driver, such as the DEC 21140's. I haven't done any testing, but I've been very impressed with mine. John