While I dissagree with "Rhyno's" analogy regarding these VSM's for HT applications, I think I might be of some assistance with comments...
...I've had the Merlins, as well as the very very similar performing SF Electa Amators over the years. I am also an avid custom home theater guy, and like to think I know very well what works best and what doesn't for high end performance from HT applications. I used the Merlins for HT dubties to excellent results, albeit in a smaller room than most might end up using them in. The room was a bit more forgiving of speaker placment than most smaller rooms, largely in part due to the openings at one end of the room, effectively making the room acoustically larger than looks would appear. The key to making those only modestly sensitive and efficient "traditional speaker design" speakers such as the VSM's work well for HT dubties, is to use them in a set up that places the listeners acoustically closer to the speakers proportionatly than the speakers are to the boundaries and/or ceiling! Basically, making you hear more dirrect sound before you hear reflected sound from the rooms boundaries. Without heavey acoustic treatments or considerations covered, this is the best kind of situation acoustically for HT dubties for this kind of speaker design! In this kind of situation, which can be achieved with proper set up in a larger room as well if careful, it makes for a much less diffused, blured, and more dynamic sounding speaker than would otherwise be the case in a poor set up with them! Usually, Diappolito, horn, active or other designs tend to be more effective, coherent, dialog friendly, solid, focused, and stronger for rock and HT applications overall, especially in rooms that are going to have you hearing more reflections mixed virtually simultaneously with what's coming from the speakers. In rooms where you do have to content with quick arriving first order reflections and such from the walls mixing with the sound too early with your speakers sound propegation wave, often it's the case that indeed more focused and frequency reinforced(i.e, tandum or multi driver design speakers such as THX, Diappolito and such) speakers tend to be more effective for HT purposes. THX understands this principle, and blesses it's speaker designs accordingly with licensing. While a VSM wouldn't pass mustard as a THX approved design, it would work in a smaller acoustic space very well with great results(still played as "small" mind you for HT dubties...A MUST!), or, again, if your have them set up where you're not sitting across a room from them with a low untreated ceiling to conted with mixing the sound all up, as well as sidewall colorations!
If you notice, THX select speakers are "dubbed" as such with the same kind of layoout as the VSM's employ(traditional design), but must be recommended for "smaller rooms" and acoustic spaces, where you're going to hear more of the speakers sound before you hear the room reflections in time domain. If you keep this in mind when considering using the VSM's, I think you'll do just fine with them. But, get em set up in the wrong set up/room situation, and they'll sound too laid back, too open, not focused and solid enough through out the middle and upper registers(and even the upper bass), too smeared and unintelligible, and basically NOT SOLID SOUNDING ENOUGH for proper HT applications! If you set em up in the right environement or room setting, with proper acoustical implementations or considerations you can avoid all these problems,and a speaker design such as those will work wonderfully!
Basically, they're excellent sounding speakers. There are faster, more dynamic, and more focused sounding speakers out there, which will definintely be more flexible for more applciations and acoustical environments for HT dubties than your VSM's, but you can overcome most of this to satisfaction indeed if you knowwhat you're doing!
Hope this helps.
