I experimented with adding wine and dark chocolate to a sauce. The result was generally OK, but the wine was not strong enough in comparison to the chocolate, I would have liked more of its taste to come through.   I knew that I will need a strong, assertive flavor for this combination, so I got a bottle of dry Cabernet Sauvignon, the label called it "spicy" and recommended it for dark sauces and beef dishes. But when I tried the wine, it turned out to be OK in taste, but too light for this application. I would have liked more bitterness and earthy notes, less fresh/sour taste.   What could have helped me find such a wine? Which grape variety (or region, for wines sold by region) would have been a better choice? Are there other signs which would have indicated such a taste? For example, I know that a Gran Reserva wine is supposed to have a better, smoother taste due to better production, but would it also have predicted a wine with a heavier taste? Would barrel-aged wine have had that taste?   If possible, I would like to hear about European wines, because I pay less for an European wine than for the same quality imported wine. But if you have continent-independent advice or can only name wines from other continents, that's still OK, there are lots of imports here.  
A very good choice would be the Amarone. It's an Italian wine from Veneto (north-east of Italy). Its flavour is quite bitter (actually, the italian word "amaro" means "bitter". We could translate "amarone" to something like "big bitter"). Its typical alcohol content is between 14% (it's the legal minimum, actually) up to 16% in some cases. A good match is to taste it with chocolate (extra dark would be preferred), so I think it should be suitable for your sauce. 