The original
is playable as-is, but there are some minor things that could need improving. For example, Intel could be much improved (Puppet Political Parties is exceptionally powerful, just to name an example), Point Defense is too uberpowerful (so fighters, combat sats and seekers become basically useless when PD is first fielded) and the Quantum Reactor is too bloody cheap for such a powerful device (never having to resupply
is powerful, and it only takes up a small space).
Alternatively, instead of looking for mods which balance out stock, you could also go with one of the themed mods. Of course, the Star Trek Mod is an easy example, but you should try the Carrier Battles Mod if you want good fighter combat, the Dark Nova 4 mod for a heck of a lot of hulls (and lots and lots of other new stuff, but the hulls are probably the first thing you'll notice) or the Eclipse Mod which makes the game slightly more realistic. Last but not least, I recommend the Adamant Mod, which is too much to explain in a few sentences - but lemme just say you can also play as a race of organic sentients (i.e. sentient plants, or living spaceships, et cetera) and even as a race of magic users.....
(P.S. Would that be
this Empire you're talking about? Would you recommend it?)