Just another opinion that the 50 cm is likely too large for you.
Any contemporary road bike will feel good the first time you ride it, until you have ridden some other bikes to compare it to and have some experience to draw from. Sometimes you won't know there's a problem unless you take it out for a long test ride. If it is possible to rent or demo the bike for a 30 to 45 min ride, take advantage of that.
Generally speaking, I find reach to be the most important fit component on the bike. Usually, if you find a bike that fits your reach, you can adjust the saddle height to the appropriate position.
The rule of thumb given in the above article is very useful as a starting point, but don't feel like it's set in stone. People have different pedaling styles, not to mention little quirks in anatomy that will make it appropriate to deviate from the formula to some degree.
Living life like there's no tomorrow.
http://gorgebikefitter.com/
2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS