I would reccomend this Mod.
I've been playing this mod for a couple of weeks.

1. Some new units which look stunning. Roman auxilia in green uniforms. Gaul warband with some great new shield designs.

2. Roman factions get Funditores (slingers) instead of archers until the Marian reforms. If like me you found archers a bit uber in the vanilla version you will like this.

3. Population growth has been slowed and building build times lengthened by 1 turn.
a) Marian reforms arrive much later. I've never had this happen before 200BC using this mod and in one campaign this did not happen until 163BC.
b)Fewer problems with squalor means less micro-managing of your cities and more time spent fighting.

ZOR - Zones of recruitment and several other new inovations.

This really is a better gaming experience than the vanilla game. Try it.