I'm getting a new desktop this/next week... I really would love to be able to play Empire... although my first priority is milking the shit out of Medieval II like I did with Rome: Total War (although I feel I haven't played Barbarian Invasion enough...).
Also this was my first time conquering the whole world. Conquering the whole world in R:TW just got boring =/ I kept restarting campaigns over and over and after dominating all the major factions (Rome, Egypt, Carthage, possibly Britania or Germania, depending on how well they do, and if I chose/could have expanded into Europe... which I almost never do, since it's in Greece and the East where all the money is at... Anyone remember the scene in Rome season 2, where Mark Antony, Octavian, and the other guy divide up the lands? XD)
I loved playing as minor factions like Armenia, Numidia (oh god, I have such a great comeback story. Losing my Egyptian bordering settlements, losing a few settlements to Carthage, and having -10k money, I placed EVERYTHING on taking Carthage... which was no easy task.) I personally had to lead victory after victory, with my slowly dwindling force (which was tiny in the first place). I decided that since I have inferior numbers, I HAD to get to the bridge, and remembering having to fight one battle on an open field, outnumbered, with the enemies having ELEPHANTS. I lost a shit load of men after that, but it was a miracle I surivived (spamming Numidian javelinmen, the only unit I could pretty much recruit against elephants). Once I got to the bridge, two decisive victories, and I attacked an near empty Carthage, with reinforcements beginning to appear. I quick saved, auto resolved just in case the AI could handle a siege battle better than me, and it WON. I quickly exterminated the population, which brought up my treasury into the positives again, and retrained my entire army back into a full stack, and crushed Carthage. After that I was able to raise Numidian Legionaires, and begin my conquest onto Italy, crushing the Scipii, Brutii, and getting bored once I got to the Julli).
... oh back to the original question, how good of a computer do you need to be able to play Empire, on low settings, and NO LAG (Jesus, I can't wait to get the new computer, so I could actually fight the battles on Medieval II that require micro management).