M&K MX 5000 THX MkII vs Velodyne HGS-18

They are both great subs but if you are 70% HT then definately get the HGS-18. It has tons of extension and if you set the crossover low enough it works very well for music.

scrap both of them and go with a pair of HSU TN1220's with the 500watt amp, get better performance and pocket some cash to boot.

Both are excellent subwoofers. I have had both in my system. In my opinion the M&K sounds a little more accurate on movie soundtracks. I prefer the velodyne on 2-channel music. I currently own the M&K 5000 MKII

Kgb540 is right on with the recomendation of the HSU subs. I have a HGS-18 but I also have a pair of the HSU TN-1225 that I decided to add since I had a extra amp lying around. They are great with movies but I still only use the HGS-18 when I am just listening to music. If I were forced to choose and listened to mostly movies then I would use the 2 HSU subs and hold on!!!!!! I picked up the pair brand new for $600 out the door without an amp and the Parasound sub amp I used with it only cost me $500 but the extension for home theater using multiple subs is unbelievable. Definately give them a try.