Distant Stars is a really good mix of all 3 more or less with some added tech changes and a few new strike craft.
I think that it is the basic mod that everybody need to have... several element of it are found in other mods but these mod simply expend the original game without adding new races...
For races based mod, it is all related to your personal taste that we don't know...
Some interesting links :
- The Best Sins of a Solar Empire Mods : http://www.brighthub.com/video-games/pc/articles/70455.aspx
- check out some of our favorite Sins of a Solar Empire mods : http://www.gamesradar.com/f/mods-of-a-solar-empire/a-200805051546549036
7DS was cited in the post up... the old version, 7DS 2.1 for sins 1.05 remain a "hot" mod... http://solar.filefront.com/files/Sins_of_a_Solar_Empire/Modifications;10371 ... you can download it at http://www.filefront.com/13863696/7_deadly_sins_2.1.7z/ ( already download 157 time these week ) but if you don't wish/can downgrade your sins version, best to try other mod for the time being, trying mod is the best way to find something that you will like... 7DS 2.5 ( for last entrenchment version ) will soon be in beta with a possible release around the end of the year...