ML320 vs. RX300 vs. MDX

Well.. we plan to be in the market for a used car... Does anyone have reccomendations between the three? (All sub-40k mileage)

1) 00-02 Mecedes-Benz ML320
2) 99-02 Lexus RX300
3) 00-03 Acura MDX

I have heard that the ML320 build quality is crap, beyond horrible! The RX revs wayyyyy too high when on the frewway (4000rpm+) and I've seen that the MDX is 6-7k more expensive than the rest but its a honda and you cant go wrong with one of those.... This is gonna be my moms car mainly but it might be my weekend car... you never know... but if you have experiences with anyo f these cars please post them and also if you have a reccomendation... please post it..

Thanks,
Mun-G