$20 for the extra 200MHz is a good deal and not a waste. Comparing the Xeon to the Core i5, they are both technically the same, the only difference between Xeon and Core i5 is Xeon supports ECC and are better picked as they need to be in a non-stop working environment. With proper cooling then it doesn't matter what CPU you get, both should last quite some time. Also ark isn't meaningless, it does provide some important features to the CPUs you want. The Xeon has 8MB of smart cache and 6MB for the Core i5. 8MB are usually found on the Core i7, so basically for that Xeon, what you're getting is a Core i7 for the price of a Core i5 with HyperThreading disabled. Core i7 has HT enabled. Price difference between these 2 CPUs is about $2 bucks.
http://www.newegg.com/Product/Product.aspx?Item=N82E16819116989
http://www.newegg.com/Product/Product.aspx?Item=N82E16819117319