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 
ksmcalley
imhififan - Yes this is a passive subwoofer.

soix - Yes I get it, but I just fell into this opportunity really cheap!

timlub - Thanks for the recommendation.

My next question for the collective is:
Do I need a specific subwoofer amp or would a general powered amplifier that also has a sub connection and has the correct connections work.  By the correct connection I mean taking a subwoofer in signal as RCA an have a wire output to the subwoofer.  Thanks, Kevin
Soix
Its not really $300 though, that's the sellers opening bid, true it may be no reserve but his bin is $539 which is more in line .

I would say you should stick to a dedicated subwoofer amp for best results as you are only going to need the lowest parts of the frequency not the complete full range. Not sure just how an older passive sub would handle that tbh
Do I need a specific subwoofer amp or would a general powered amplifier that also has a sub connection and has the correct connections work. By the correct connection I mean taking a subwoofer in signal as RCA an have a wire output to the subwoofer.
You can use your receiver speaker output connect to the passive subwoofer, please refer to page two of the PDF file:

https://www.paradigm.com/downloads/OM-40SB.pdf
http://www.audiocircuit.com/A-Images/AA-Brands/P/Paradigm-PAU/SB-100______-F-006-906-PAU.jpg

Or, you can use a power amp with volume/gain control or a subwoofer amp connect to your receiver "sub-out" to power the passive subwoofer, you can turn off / bypass the crossover in the subwoofer amp because the passive subwoofer already had a built-in crossover.