i agree w/sean - let your ears be the judge. i am not knocking rel or the other powered subs out there, i yust think they are not cost effective - it's more expensive to get accurate, undistorted, deep bass out of a smaller box than it is to do it as vmps does. it's true that it's hard to fit a pair of vmps' larger subs into many decors.
as far as integration, i believe that having a hi-quality, flexible x-over is the key to using passive subs. the marchand is both. i also believe it's far better than the electronics built-in to most powered subs. and, you have your choice of amplification.
the marchand's flexibility has allowed me to successfully use thiel 3.5's & meret re's w/my subs, as well as audition proac tablette signatures, totem arro's, & even some nht super-ones. i'm looking forward to my brother-in-law bringing over his proac 2.5's to try.
as far as a mfr having negative things to say about vmps, i have spoken w/several over the past few months, and they all had nothing but good things to say about 'em - melos, cary, newform research, rogue audio... also, a couple dealers (who don't carry vmps) had positive comments about 'em.
again, these are my opinions only - ymmv.
doug