The only Signature in the DTD area I would suggest is The Dining Room at Wolfgang Puck Cafe, but it isn't very high on our Signature list. What time La Nouba performance are you seeing? If you plan on seeing the 9:00 performance, I wouldn't plan to do a Signature that night. We usually expect to spend about 2 hours or so on Signature meals. This means you would have to get an ADR no later than 6:00, which means you have to be at the restaurant by about 5:45, which means you have to be at the bus stop no later than 5. And if you plan on having a Signature somewhere other than DTD, tack on an extra 30 minutes in travel time. Now if you add in the time it takes to shower/freshen up, well that doesn't leave a whole lot of time at the parks that day (you really would have to start heading back to your resort at about 3). If you are planning to see the 6:00 show, you can plan a Signature basically anywhere for anytime after 9.
Personally, I wouldn't do a Signature on a night we plan to see La Nouba. I would spread out the nicer parts of your trip, instead of doing them all in 1 night. I would make an ADR at either Raglan Road, Bongo's or Wolfgand Puck Cafe on a night where you see La Nouba and then save the Signature for a different night.
When it comes to Signatures, our favorites that take the dining plan are: Citricos (GF), Flying Fish (BWI), Artist Point (WL), Jiko (AKL), Bistro de Paris (EPCOT, not sure how it is since it started to take the dining plan). If you are not tied to a dining plan, I would also consider Shula's and bluezoo (both at the Dolphin).