I rather suspect that the Korx were generally willing to trade with anyone they could; it's their ethics and/or morals that placed them into the evil category, not their trading partners. They're described as being willing to do just about anything for money, which strikes me as more 'evil' than 'neutral' on the ethics and morality scale, and I can't recall there being anything in their description indicating that they would prefer a certain set of clientele based on common alignment. Granted, being 'evil' probably isn't the best way to make trading partners, but their kind of evil always struck me as the "there is nothing I won't do for the right price" kind of evil rather than the Drengin "torture and kill for sport" kind of evil or the Yor "wipe out all life in the galaxy" kind of evil.

Speaking of races I am more so hoping for the custom race section to come back up and running that way we could add back the old civilizations that won't be added in to the official release. But this is Galactic Civilizations so of course there will be custom races. 

Pretty much this.

They have no ethics code. They will do anything for money - including as the description in GC2 said, sell their own family members off for money.

It's like someone is a psychopath or had antisocial personality disorder, but on a widespread scale.

SE3 had the single greatest random event I ever saw in a 4X.  Planets have happiness.  Conquering a planet sinks its happiness to ~30%.  You must laboriously build system-wide joy facilities, set that planet's tax rate low, and garrison it with a surviving damaged troop, to coax its happiness up.

• If planet happiness falls, it riots.  A rioting planet produces 0.
• If a planet is in riot for many turns ... it secedes from your empire and becomes a new AI, which promptly declares war on you .  See Scotland vs. FUK (F = former) later this week

In dozens of SE3 games, I saw this happen only once, ever!!  I spent many games after that trying to recreate it!  AFAIK, SE4 and SE5 eliminated that possibility, which was tragic.

I would pay money for a 4X that allows this to happen!!

• Corollary: The "Rebellion Start" scenario.  There was a sim of 100 AIs against each other.  It was long and bloody.  One AI ruthlessly exploited its conquered colonies, until finally ... a colony rebelled and seceded from all AIs, and became ... You.  On turn 0.  Welcome to the game.  You are surrounded by hostile AIs.  You have just declared war on one of them.  It's coming to take you back.  Fight.

I'd pay money to play that, too.  It's like Robotron dropping into a Mikey level with brains and cruise missiles!