Got an Onkyo 600 amp , but have a cheapo Yamaha sat/sub. Also have around £500 to spend I think that a sub would improve my system over new sats at the moment and have read a few threads with interest. It seems the only choices are MJ acoustics (either Pro 50 or Pro 100) or the cheapest REL, or possibly the Anthony Galow sub, although already had a bit of a bad experience with them. My demands are movies only as I have a dedicated music system and I am mostly looking for slam and grunt, rather than any subtle stuff(, although I probably have never heard a good low rumble atmospherically because my existing sub is so bad) Can anybody recommend some to listen to. Also my amp has a choice between 80,100 or 120 Hz crossover. have tried all three and they do seem different but not sure which one I prefer. Is there a recommended setting I should use, and would this change with a new sub. Really appreciate any advice, and thanks in advance.