How do I get a speaker with the bass slam of my el cheapo ear buds...?

in a word, phone is a poor pre-amp.  It can only drive very high efficient earphones, usually cheap.  Because cheap ear bugs don’t have good control, sounds are usually heavily distored.  With strong bass does not mean accurate bass.

you need a good preamp.   But your phone may not have a good impedance matching wih high-end preamps via analog signals anyway.  That’s why people need to buy good sources, like hi-end cd transport or digital network player to get a high quality sound.  

But if you would still want to use phone and hope to get a good sound for your stereo system., you can try using a good headphone amp as pre-amp, then connect to your stereo.  Or you can go “digital” transaction method.  i.e.  using a portable DAC/headphone amp.  like Audioquest dragon fly or Fiio’s DAC/headphone amp.  Also make sure your stereo system can deliver a good bass slam first.

The portable DAC/headphone amp can also be used for car stereo purpose.  Good luck.

Dear d2girls, you are not logically wrong.  However,  I would be very glad if you can provide some good doable suggestions on how to improve the sound from a phone output.  Happy Friday every one!

By the way, I saw that you did purchase Krell FPB400 around Sep, 2014. You used to drive your Legacy speakers using a Nak receiver long long time ago.  It seems that you have a steady audio growth path with you. You even started a  “slam” topic before. You should have more knowlege than many (if not most) of us to answer your own question.  

So, afterall, you want to let the phone to drive a series of state of the art preamp, amp and speakers and get a nice slam effect like the phone drivig a free earbud.  Thank you very much for your experiment.  It showed to all of us that it does not work.  :) 

@m-db 
Thank you for your understanding. 
@glupson 
Obviously I got same feeling as you did.