Yes, 1/700 is the way to go if you want all the WW2 USN CL's . Between Niko, Dragon & Pit-Road you can make'em all, even an Omaha class.
I started late buying Niko models. My Helena was $71.10 after shipping. It was a single item purchase, rare for me. FreetimeHobbies has the Niko line.
Back to Titanic...
My previous reference to Megahobby as a pre-order shop was done on purpose. AAA Hobbies is the "front" for MegaHobby. (The Megahobby "store" is the entire rear section behind AAA Hobbies.) Mark (mstazz62), is a major patron over at AAA and is there on most Saturdays. Shameless plug... my bad.
Nino