Hello, I've got a similar problem stereo wise as there is just no way to
get those tiny speakers to give much bass, plus if you try they start to
bottom out and distort, as you have already found out. More amp power
really won't solve the problem. I purchased an Audiovox B-200 powered 8"
subwoofer tube a few weeks ago at a pawn shop for $35 (Supposedly new at
Wal-Mart around $80-$90). Moved it around to various locations in the van
to see where it would interfere the least while camping - just the thing
itself, it was not hooked up as the goal was to determine where it would
work space-wise best, then wire it in. Today it was installed behind the
passenger's seat sitting on the floor using some velcro on the feet as I've
got a piece of automotive carpet layed over the floor. I imagine some
no-slip feet would work well also. The wires were run under the passenger
side carpet above the wheelwell, and the wiring harness hangs out over the
battery box. This way all I have to do is unplug the wiring connector and
leave the subwoofer out when I go camping with others and need all
avaialable space. The 4" speakers are stock, may upgrade in a while. Vast
difference in sound with this bass tube. It's about as cheap a powered
subwoofer as you can find, but the Westy is so noisy it seems foolish to
spend lots of money on expensive speakers so they can just get drowned out
by the road noise . . . .  The primary goal here was not volume, it was to
make my stereo sound better than a cheap AM radio. That goal has been
satisfied. If volume was the goal, then a powered subwoofer combined with
filter capacitors in series with the stock 4" speakers to cut down the
amount of bass going to them would be a better choice.