hmm. I use to answer on right question, but it seems that in this case perhaps there are different solutions. First of all DIR-655 has 3 antennas. So you can use one of them with for example Yaga this baby will send signal through concrete, but can it receive ? You need to test it. 2nd option is connect cable and extend antenna connection.
Range extender may be a problem.I guess that you know how it works. But in case, roaming,channels propagation etc. It is good solution in big area, or like tunnel environment.But home, I do not think so. Try borrow from someone stronger antenna , perhaps it is enough for you.