i have good results using a pair of vmps larger subs & a marchand deluxe version of their xm-9 x-over. the marchand has *wery* flexible controls, & w/24db/octave slope, can seemlessly mate the vmps' w/most anything. i've successfully used both thiel 3.5's & meret re's w/my subs. also successfully demo'd proac tablettes, totem arros, nht super ones. i hope to demo some proac 2.5's, & i hope to purchase some newform research's, not sure of the model.
vmps (a full-line speaker mfr, btw), will offer good set-up support for their subs. i feel they are more accurate than any sub at anywhere near the price - my sub system, consisting of 2 larger vmps', 2 adcom gfa555's run bridged-mono, & the marchand x-over, is about the same price as *one* top-model velodyne, w/all its amplification/electronics included. i woodn't trade my system for *2* velodynes.
oh yeah, i'm also a firm believer that 2 subs are needed for proper 2-channel audio.
regards, doug