And they are twelve inch speakers. I want to put a Jensen in there. But musicians friend says they are 100 watts, and my amp is only a 15 watt amp (tube). Would this be a problem.. ?
Follow me on twitter and junk @GodDammitZack

Epi Les Paul Std w/Duncans
Cry Baby From Hell
Marshall JH-1
EHX Metal Muff
MXR EVH Phase 90
Carl Martin Classic Chorus
EHX #1 Echo
Ibanez LU-20
Dunlop DCB-10
Crate V50112
Tascam US144

from what i understand, you can have a speaker designed for higher wattage in a lower wattage amp, but the same doesn't hold true for a low wattage speaker in a high wattage amp.

just make sure the impedance all works out.
My name is Charlie.

Gretsch Electromatic Pro Jet
Fender Deville 410
Electro-Harmonix USA Big Muff
Digitech Whammy IV
MXR Micro Amp
Dunlop Crybaby Wah
you'll be fine. As lazlow said, make sure impedances work out, and know that you won't get any speaker distortion, but that's kind of a lost art anyway.