These all sound very very interesting, the HW series i have and yes they are Excellent!!
Some of the others are new to me, the Master of Orion, i have heard of but havent played, and the Genesis and Nexus titles i looked up after you mentioned them, they look different than Sins, and that is both a plus and a minus, haha, i like the difference, but dont know yet how they will play, but thank you for mentioning them.
FreeLancer is another new one, and the GalCiv series i understand is also very excellent!! And on Stardock to boot, so that is a plus, easy to get and try.
Some of the others i havent had a chance to look at yet, the Hegmonia titles, but the YouTube videos look very promising, and Mass Effect sounds neat, but i dont know if my machine is powerful enough, im running a dual core 1.8 intel with 3g ram and a 256 Nvidia 7100 video card, so my machine is reallyl just middle road for games, if more than enough for the internet and local apps.
Eve i have tried, but yes, the trial was very cool graphics, but the learning curve was very steep, i couldnt figure out what to do, i know i sound stupid, sorry, but it was more than the casual game that makes Sins so very marvelous, so much is already controlled by the ai that it is almost cinematic, like playing a space battles movie!! Haha, i hope i havent offended anyone with my comment, but i love Sins for that, it is easy and what i would call accessible!
At least for my casual style.
I dont mind long or involved games, but i usually only have about an hour to play a day, and maybe an hour for email and the like before having to get back to the real world, i like a lot of people probably have too many committments there. Anyway, i wanted to say thank you to everyone for their wonderful input and suggestions and ideas and say i will look forward to trying some of these and i will get back to you and let you know what happens. 
Take care and keep gaming and keep modding!! Forever!!! Haha,
-Teal