martin logan grotto or klipsch subwoofer

Looking to buy a used sub off audiogon. I like the martin logan grotto and there are a few different klipsch that I have seen for sale. I would like to keep it under 500 used. What is the better choice between these two brands. I will use it most for music and I am most interested in tight accurate bass and not as much into boomy bass. thanks
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Thanks Bob, I ended up going with the klipsch and the bass is awesome
Which Klipsch sub did you buy?

Was it one of the RT or RSW subs?