Yes you can, but it will be a different kind of bass.You're not going to get a lot of bass from 6-1/2" woofers. More power will help some but there's no replacement for displacement.
Physics dictates that in order to create sound from a loudspeaker you have to move air. A large bass speaker can move a lot of air with very little excursion. A small speaker can also move a lot of air, but it has to move a long way in the same amount of time to do it. I find that smaller speakers tend to sound a little punchy (if that's the right expression) when driven hard at low frequencies. Big speaker bass tends to be more relaxed, deeper and smoother (I'm an engineer and I try to avoid using non quantifiable terms like that - but you get my point). The small speaker will suffer from overshoot at the extremes of movement - oh yes it will (physics again). So everyone is right.