nothing will touch a pair of vmps subs w/decent outboard electronics at anywhere near the price - twice as much $$$ won't do it, imho. but, if ya like yer current sub & it integrates well-enuff, the best ting ewe can do for yerself, imo, is get another to match yer existing - two subs are the way-to-go for audio - better soundstaging, less distortion for the same wolume-level, etc.
Looking at a new sub for ML
I have ML Aerius I, with bak vk200 amp and nht 2swpi sub; believe it or not the nht 2swpi was better than the sunfire, velodyne, paradigm; when it came to music; not trying to insult any of these subs/sub owners, but for the money nht was better. The system sounds great but I would like to upgrade my sub. Thinking of the REL storm III, Genesis 928 or something in the $2000 range new or used. I do use the system for HT, but when it comes down to it music is my love. Now can the 928 intergrate(accurately, detailed base) into the system(w/ML aerius i) better than the rel storm III. I've never listened to the 928. And the rel I did hear was not setup properly. Help. Thanx