Thanks Russell; 51/2 foot iguana lizards? I'm scheduled to holiday in Costa Rica around xmas, I'll keep a sharp eye for those maneaters! Sistering joists just means you attach a 2x6 joist side by side with the existing joist. There is a little trick to it, you have to knotch one end but there are plenty of framing books in the library that explain it. I actually used 2x4's they"re cheaper. Believe me you will notice a difference. Lots of bass energy leaks through the floor; more than you would expect. When I did it I had the Valencias in that room and noticed a real improvement. Sprung floors have lots of give that soaks up bass, this tightens them up. The acoustic insulation kicks up the absorbtion of fundamentals and the sheetrock adds mass. To me it was like buying a 4 fold better amp. Keep us posted, J.R. People who hear the Pi 4's in that room are amazed at the prodigious bass output.