parma for 1 night...where?

You don't say anything about the type of accommodation you're looking for, price range, etc but I stayed at the BB Rubra a couple of years ago for one night and loved it. It's more of an apartment than a hotel room, but it's a short walk from the main square as well as the lovely park, and was ridiculously reasonably priced and anything you need in short distance. Since you're staying overnight, I STRONGLY suggest you take a free tour of a Parmigiano-Reggiano dairy through the consortium if you can. You can take a taxi out to the dairy (not much over 10 euros if I recall) and spend the morning seeing this wonderful product being made. One of the highlights on my numerous trips to Italy/Europe.

We are looking to stay in the center of town. Since we will only be there one afternoon and night, we want to be centrally located. We have been looking at R&B Opera Hotel, Hotel Torino and Romeo & Guilietta hotel. Has anyone satyed at any of these? Is parma a good choice to stay over for one night on our way to venice? Another town recommendation?

We stayed at Hotel Della Rosa Prati right in central Parma and loved it. Highly recommended!

A normal route for travel by train from the 5 villages of the the Cinque Terre is often: Village to La Spezia La Spezia to Pisa Pisa to Firenze Firenze to Venezia SL,
all in something over 4 hours. The train from Firenze to Venezia will likely call at Bologna and Padova on the way to Venezia; Parma is some distance west of Bologna, beyond Modena. Not exactly on the way although it is possible to reach Parma by Regionale train from La Spezia. Many people will say that just over 4 hours in a go on a train isn't too bad and and maybe you could push on and get to your destination and enjoy more time in the magnificence that is the most Serene City.