I own a copy of Spartacus: A Game of Blood and Treachery, and I really like it. Chains to Champions seems to carry the same (albeit simpler) gladiator style gameplay structure as Spartacus. Is it worth getting this game if I already own Spartacus? What makes Chains to Champions a different worthwhile purchase to someone who already owns Spartacus?
Definitely a different feel/audience for these two.
General game-play: Spartacus is definitely a more mature (not just card text), back-stabby game than CtC. That's not to say CtC doesn't have a bit of "take-that", it just has less points where that is available/desirable and it usually takes the form of bluffing rather than pure back-stabbing. Spartacus has the phases (market/combat) structured in a continuous loop whereas CtC does it as one phase after the other.
Components: Spartacus feels more like a polished game, one you would be able to break out with a group of friends or with a group of strangers at the FLGS. Whereas CtC seems like non-AFOLs may view it as a "kiddie game". CtC has way more options on equipping your gladiator with weapons and armor and if you like LEGO mini-fig bits(I do) you'll find that CtC has great appeal.
Combat game-play: I think both games are decent in their own right. It is hard to improve on the simplicity and elegance of Spartacus' attribute/dice mechanic, but then again you may be looking for something a little "crunchier". CtC provides this through special abilities and card combos. Here's a quote from my CtC review:
Actual attacks and damage calculation are a little math intensive compared to other games of this genre, but nothing too complex. There are quite a few nuances, especially when adding in Specials and Academy cards so take it slow the first few times you play. The “scale” of attack to defense is not intuitive (ie, it seems easier to attack and do massive damage than defend) so hopefully more plays will allow us to calibrate our tactics.
Overall: I'd say they are different enough to warrant purchasing CtC, but that's just my opinion.