I'd like to utilize my sister's old hifi stereo system with my new record player I got as a gift. Is this all I need for now?

Got a record player as a gift with one record (Aphex Twin's Selected
Ambient Works 85-92) back a while and haven't been able to use it
properly as I don't have the right speaker set up. But wait, maybe I do:
I could utilize my sister's old Sony LBT-D270 compact hifi stereo
system couldn't I? And all I'd need to complete this connection would be
a preamp, maybe? Something like this?: https://www.amazon.com/Pyle-PP777-Electronic-Phonograph-Preamplifier/dp/B09QHB8SHR

I appreciate greatly any help I get with this. Feel free to give me any sort of feedback here. Is this that simple?

You could get the RT82 and an external preamp, like a Pyle or ArtDJPre

IMO Project > Fluance with the U-turn a distant third. But if you want to stay under 400 get the better Fluance (RT82) at 299 plus an external preamp