Okay, I'm thinking of starting a new timeline project involving the Early Roman Republic. My idea is really quite simple: Rome has to focus more energy on Italy, slowing its conquest of other regions, because it has a serious rival to contend with and can't turn its back as much. What I'd like is some help from the AH community as to who would make for the best candidate: obviously, the Etruscans and the Samnites are reasonable, but the former is already decaying by the time I hope to start me TL (5th-4th century BC) and the latter, while formidable opponents and powerful militarily, lack the staying power necessary to be a long-term rival, like Carthage was. A city in Magna Graecia would be an easy choice (and there's no real shortage of candidates, such as Tarentum or Syracuse for example), but Roman intervention in Magna Graecia will inevitably lead them into conflict with their neighbors, especially if it's a Sicilian city.
So, I'm looking for a rival in the north. The ones I'm thinking of (although I need to reread my book for this) are either Veii, which was a strong rival (it was an Etruscan city IIRC), or Capua, which if I'm not mistaken was the most powerful rival Rome faced in the region for a while.
So, any thoughts?