Those dates are some of the busiest for travel between those cities, so booking as soon possible is a good idea.
That said, Iryo is not yet selling tickets for those days. (Mid-December is the latest I can book now.) And Iryo is together with Renfe the main operator on those routes. (Avlo and Ougio are "low cost" companies.)

I know that people are saying that Trainlines is trustworthy. But they are just a reseller, however you look at it.
Personally, I'd keep an eye on the Iryo website (https://iryo.eu/en/home) and compare prices with Renfe once Iryo starts selling tickets.

For what it's worth, Renfe (renfe.com) is already selling tickets now for those dates (but maybe not for all trains), and the prices are a lot cheaper than what you mention:



Barca (actually, "Barça") is the football/soccer club (FC Barcelona), but never the city (Barcelona) itself.