Professional business network Xing announced this week that it has acquired Amiando, an online event registration and ticketing site, for €5.1 million (approximately $6.7 million) initially, with an additional €5.25 million (approximately $6.9 million) payable on March 31, 2013, if various terms are met. To fulfill those terms, the current management team at Amiando must stay on board and various revenue and profit targets must be reached.

Amiando CEO Felix Haas, like the company’s entire staff of 35 employees, will retain his position.

“From now on, we can offer [Xing members] all of the services they need including efficient registration, ticketing and billing,” said Stefan Gross-Selbeck, CEO at Xing. “This in turn allows us to tap into a highly lucrative and market currently experiencing rapid growth.”

Headquartered in Hamburg, Germany, Xing can be likened to LinkedIn here in the states. It is a social network for business professionals that hit the 10 million member milestone just this past September. That’s still a far cry from LinkedIn’s estimated 75 million members, especially for a company that was founded in 2003, but slow growth is better than no growth at all.

Xing is no stranger to strategic acquisitions. In 2008, the company spent $7.5 million ($4 million cash upfront plus $3.5 million in earn-out) on socialmedian, a personalized news aggregation site.

With the purchase of Amiando, Xing continues to flesh out the offerings of its business network by joining forces with a European-based ticketing site. Based in Munich, Germany, Amiando organized and processed 100,000 events on its platform in 2009.

As we noted in early October, when U.S.-based competitor Eventbrite raised a solid $20 million Series D round of funding, Amiando is already one of the most-used event registration and ticketing sites in Europe. With that funding round, however, Eventbrite acknowledged that it would be expanding more aggressively outside the U.S., the country currently responsible for 85 percent of the site’s gross ticket sales.

With Amiando’s platform now leveraging Xing’s large business network, Eventbrite may have a harder time penetrating the European market.