Sell the groupo complete on ebay including bottom bracket/headset if it as all super b stuff. You will get the most selling as a complete group. It looks you have a turn key bike that is ready to ride. I doubt Ultegra would be worth the cost of upgrade as of now. Wear out the old groupo and find out what all the fuss is about.

I'm willing to bet you are going to have great reliable shifting with the current components.