To make long story short - friend of mine started playing bass, bought this Behringer BX1200 (served him well as begginer amp) but now doesn't like the sound of it very much. He noticed (like many users here on TB), that the aluminium speaker in the combo is crap and that the combo sounds much better with nice external speaker (4 ohm, disconnects the internal 4 ohm aluminium crap) He is looking into building decent external 4 ohm cabinet (preferably with 15" speaker). I got 2 questions: 1. Which solution is better - building decent cab, that could be later used with another amp, or swapping the inernal speaker for something better (cheaper than building whole cab) 2. Depends on question 1 - what kind of speaker should he buy for the cab (4 strings player, 4ohm cab, 15" driver, I assume front ported box, 120W amplifier - 150-200w speaker?, not huge dimensions of cab) or in case of swapping the internal speaker - what does fit the combo and sound good in it? Thanks a lot!