The Hyperspace Wars take place during Naga Sadow's reign over the Dark Lords of the Sith (Golden Age of the Sith / Fall of the Sith Empire), and he is most positively the most interesting character.
The brother and sister (Daragon twins) are just hapless young adults caught up in the middle of the whole thing. Their story is interesting, but you won't find this epic.
-5000 years before ANH
The saga of Ulic Qel Droma, Nomi Sunrider, and Exar Kun, and The Sith War, is an epic greater than the Classic Trilogy IMO. The Mandalorians enter the wars here.
It takes place 4000 years before ANH, but is dependent on the establishment of an underground Sith Order within the borders of the Republic, so the earlier stories do help with background. But THESE, these stories and the legend of Ulic Qel Droma and Nomi Sunrider are truly epic. You'll like the start, but while it's entertaining, it will seem unimportant.
The next part, The Freedon Nadd Uprising is truly awesome, and it is the HARDEST PART of the story TO FIND. Try ordering direct from DarkHorseComics.com! They might have made a trade paperback (TPB) out of it, but this part of the series was only 2 issues. They are so critical and cool though!
Then Dark Lords of the Sith and The Sith War, and Redemption will just have you floored! They so much needed to do action figures from this series, I swear!