Simple low end amp question

I have a first generation Paradigm fully enclosed chamber with 2 bottom firing ports Passive subwoofer.  I wish to hook it up with a far more modern receiver with just a RCA sub out while the sub only connect by wire.  I am told that this sub will need an amp hooked up to it to be able to fully power it and be able to use it like more modern powered subs like the other ones that I own.  Any advice and recommendations of what basic amps that I would need/should buy to accomplish this.  Many Thanks,  Kevin