May I add a subwoofer to stereo system?

Did anyone set up one or two subs to a stereo system? How it sounded? I am looking to add one or two subs to my strereo system but don't know there is any improvement. Please help.
My stereo system consist:
Speaker: Mezzo Utopia
Amps: Audio Research VT-150SE Mono
Preamp: Conrad Johnson 16LS
CD: will buy MF Tri-Vista SACD
Speaker cable: Kimber select 3038
Interconnects: Nordost Quattro Fils.
Thanks so lot in advance.