Excelsior class heavy cruisers are a development of the late 23rd century and lasted in service into the mid to late 24th century.
First conceived as "transwarp battleship" the development program was the darling of the Guns & Butter party in Starfleet. A reaction to the growing tensions with the Klingon Empire. When transwarp turned out to be a boodoggle the class ship the USS Excelsior NX-2000 was returned to development and eventually launched as the NCC-2000 a more standard warp drive and a tough, but gentlebeing commander Captain Hiraku Sulu. Heavy cruiser was firmly stamped on the class by then Admiral Jerold Ryan LaSaille
What is commonly refereed to as the "refit" started with the USS Enterprise NCC-1701-B. It was widely believed to be over engined in the impulse department. But the original ships were considered to be under powered at sub-light. Staid heads shook in disapproval of so many engines. Yet the class lasted in service into the late 24th century as a robust and capable vessel.