Recently been getting some better audio equipment, picked up some DT770 pro headphones as an upgrade along with a good amp, needless to say i dont want to wear heaphones all the time, even though they sound really good. Grabbed some 2nd hand kurzweil KS-40A studio monitors for cheap and they're giving me a pretty good balanced sound with great highs, especially for the price, but the bass is a bit lacking. I'm saving up for a bunch of stuff elsewhere so i cant really afford a new subwoofer to give me more bass, so im looking for some good second- hand options. I can use my grandfathers spare amp that will deliver enough power for the average 12 inch sub if needed however i would prefer a powered subwoofer, im also going to be using this thing at my desktop pc in a fairly regular sized room, so it dosen't need a ton of power behind it and almost definetly dosen't need to be any more than 8 inches. Looking ideally for something under £60 or so, but i can go a bit higher if something good can be found. Thanks.