Please don't confuse the i7 processors with the Xeon processors found in MacPros
i7 which are "desktop"
http://www.intel.com/content/www/us/en/processor-comparison/compare-intel-processors.html?select=desktop
Xeon which are "server" class processors
http://www.intel.com/content/www/us/en/processor-comparison/compare-intel-processors.html?select=server
You really haven't built a MacPro. You're closer to a 2011 iMac (Sandy Bridge i7) with some modifications.
Granted the MacPros haven't had a processor upgrade since 2010 (except for a minor speed bump). I'd expect the 2013 MacPro replacement will be using at lease Sandy Bridge Xeons. Xeons tend to be 1 generation behind. Current i7 is Ivy Bridge. Current Xeon is Sandy Bridge.
You might find this article interesting
http://www.theinquirer.net/inquirer/review/2157358/intel-xeon-e5-2670-vs-core-i7-3960x-review
If you look at PCs with Xeon comparable Xeon processors, they are comparable to MacPro (when they were comparable in 2010) and my hunch will be in 2013 when MacPros get replaced.