Thanks, KP for the info on ARC. I'm not a modder, so I don't know if I'll try messing with that or not. It's nice to have such a responsive and benevolent dictator leading my empire!
CaptainYar: I'm currently playing a custom race with the spore ships. They are nice in that you automatically win the planet with a single ship, but you take a econ hit due all the infrastructure upkeep with no population. I found that I needed to research the invasion techs later to bolster my defences. On the war front the three opponents and I sometime trade planets back and forth since I easily take them, but then can't defend them with such low populations. I found you have to start using some transports or colony ships to ferry in population to bolster newly spored worlds. You also need to research the advanced toxic colony tech or you only get %50 production on your new conquests.
Getting military tech is still paramount so you can eliminate the AI's orbiting ships. Unless you go for a very quick rush, as in a ZYW, the AI will ussully have something there to defend the planet.
All in all, I still have a huge population because I don't have to expend it to invade (zero casualties with the spore ships) and like you said the taxes don't get wasted with population floating in space. I'me doing better than ususal with the economy in this game as well. Of course, maybe I'm just getting better at the game.