Following straight on from Ludens, I can say I have played Hellenic, Napoleonic and Samurai and can heartily recommend all three, and also Pike and Musket (new version released today, by the way ). Going into a new era makes it an entirely new game. I've only just got around to XL myself, but my two campaigns so far have been great fun (Armenia and the Golden Horde).

Hellenic was the first MTW mod I tried, and the first battle in that got me totally hooked. Amazing new maps, really sharp graphics, new era, unfamiliar troop types, complete wow. Napoleonic gives you a new emphasis again. Samurai recreates STW with better gameplay.

All of the mods above have been easy to install. As you can probably tell, I like the mods particularly for different eras and I can go pretty much anywhere between the Greek Bronze Age, right through to the Napoleonic Wars. Given that the mods are also free downloads, that REALLY stretches your WalMart bucks into incredible value for money