I converted the ML to OEM xenon's, but for the C230 decided to go with H7 Osram Silverstar bulbs.
Osram and Sylvania are the same company. However, you are right, the usage of "silverstar" is very confusing. The US Sylvania junk Silverstars are proven to diminsh on the road visible light. They suck. The european Osram Silverstar Bulbs are NOT sold in the US. You can buy thru an online dealer like www.powerbulbs.com
Because MB lenses are pretty good, upgrading a bulb can provide only marginal improvements at best. But the euro Osram Silverstar bulbs did provide noticeable improvement of on-the-road light on the C230. They do NOT produce white light. White light on regular bulbs is produced by blue tinting which reduces on the road light! I got them at www.powerbulbs.com
and they came really fast. The bulbs are NOT cheap - but I think they are worth it.