I was hoping one of you experts could help me out =). I am confused about what freq. this sub goes to. There are 2 sets of numbers which one applies?

Freq Resp +/-3dB (Hz) 25-120
Freq Resp +3dB/-9dB(Hz) 18-150


Does this sub go to 25 Hz, or 18 Hz? or am I totally reading this wrong? =) Am very new to this HT. Oh BTW I have my Epic 80 home theater speakers hooked up to an Onkyo TXDS989 V2 A/V reciever. Does this receiver pump out enough power, or should I add amps to this set up? Thanks for any info I get! =)

Marty