Don't know why but mine sounds great in an x-cab. Alpine deck i-pod ready... ect, 4in Memphis audio m-class front and 6.5in Memphis audio m-class rear, super nice older 4 channel Memphis amp. Bridged the front 2 channels to run the speakers (works perfect and sounds PLENTY good), bridged the rear 2 channels to run the sub (10in kenwood in a 1.1 cuf box sealed). Loud, clean, bump.
Oh and I did have a tube in there and it sounded ok. Not half as good as a properly set up 10 though.