The Königsbacher brewery, which lies well outside the town center, became the Koblenzer brewery a while back. Nice looking Biergarten there. But the bus stop still carries the Königsbach title: From Koblenz' main station it's about 9 minutes by bus to "Stolzenfels Königsbach."
Koblenz is central to Bonn to the north and to the Upper Middle Rhine Valley towns like Bacharach, St. Goar, Oberwesel, Boppard, and Rüdesheim just to the south. But I don't find Koblenz all that interesting myself and would prefer a place to stay with a more historic feel. Boppard fits the bill well. And all the innkeepers in Boppard have agreed to offer their guests a free VRM Guest ticket for free rail and bus travel around the VRM zone. You can use it throughout your stay in Boppard to reach all these places, including Koblenz, quite easily, the only exception being Bonn (just get an add-on ticket for Rolandseck > Bonn to cover that segment.)
Boppard has a nice waterfront promenade with several restaurants and hotels as well as a nice town square with the same, both good spots for hanging out. Don't miss Gedeonseck, a few minutes of easy walking at the top of the chairlift ride.
In addition to the places listed above I recommend visiting Marksburg Castle (a 25-minute hike from Braubach's town center) as well as the towns of Remagen (see the Apollinariskirche, old town, and the WW II "Peace Museum") and also Linz, both to the north of Koblenz.
On the Mosel, I think I'd recommend a night or at least a multi-hour stopover in Cochem in addition to 2-3 nights in Trier, which probably is your best base for a day trip to Luxembourg.
