Is the Dunlavy SC-3A's a good speaker for HT?

MY personal experience with the Dunlavy's is that they are supeb for HT!!...Infact, often better for HT than music. They are very dynamic, fast, musical, and accurate sounding...especially with the right gear. They do what you want from a good HT speaker really.
The only stipulation is that you MUST cross them over as small on your pre/pro for movies!!!! You'll blow drivers if you do full range, and the bass will give way under too much heavy low bass with those speakers. Crossing over as "small" or there abouts, is going to do well for you. Get the sub placed well and you should have trememdous results for HT!!
Infact, a few years back at a local Home theater show, the Dunlavy's sounded best for HT over much more expensive room sysetms in my oppinion.(and I'm not a huge Dunlavy fan per se!). But, set up right, the Dun's really do well for that kind of medium, including rock and roll.
AT THE VERY LEAST, if you have the bug to try them, you shoule definitely give em a go! the set up well in rooms due to the spread out driver spacing withih an acoustical space(room). They even out well compared to speakers with single drivers in one spot, thus adding a stronger coloration/signature compared to the Dun's. Overall, they are, well, ACCURATE SOUNDING, and should be tried I think.
There are several HT magazine reviewers that Use the Dunalvy's(Steve Stone, Robert Deutsch, AVInteriors edditors, etc).
The only thing worth considering as a possible downside on buying some Dun's would be the fact that the business went under, and matching drivers might be a challenge if yours go south...something to think about. Good luck

The SC-IIIA's are almost identical to the Athena/Aletha and the Cantata. The "new owners", before Dunlavy tanked discountinued the Athena, Aletha and Cantata in an effort to consolidate the line. I can't say that I disagree with their decision. The SC-III I always found to be a bit lacking, mostly in the low-end for obvious reasons.

I use mine 80% 2-channel and 20% HT. I disagree with "forever's" comment about running them full range. I have always run the Cantatas full range without any problem whatsoever. You will loose quite a lot if you roll-off the low end to the SC-IIIA. They are spec'd down to around 30-32Hz and Dunlavy's specs are always conservative. If you select the "small" mode for your left/right the bass will roll-off around 80hz I believe. That's a lot to miss for those speakers that, IMO, can well handle that.

If you like the way they sound and I'm sure you're getting a good price go for it. I don't think you'll regret buying these speakers.

Actuall "Rap", there's a RATHER LARGE difference between the Cantata's and the SCIII's(which is, first, what I was refering to in regards to setting as "small"). The Cantata's, I beilive, have a much bigger bass driver on the bottom of the speaker, and it's PORTED!!!!!...making it a very very different design than what I'm talking about. Second, the SCIII only has 2 6" bass drivers in a sealed enclosure, WHICH IS NOT CAPABLE OF PROPERLY(NOT EVEN CLOSE!) handling FULL RANGE DD/DTS bass!!!!....NO WAY! I know FROM FIRST HAND EXPERIENCE that if you run those SCIII's full range for movies(or even heavy rock,techno, rap, etc), you'll distort the bejesus out of them, it will sound mushed, "bottomed out", strained, and begging for relief!!! I have sold the Dunlay's since 1996, have been to the factory and talked with John personally on a number of occasions! Infact, let alone movies, I can EASILY run the much much bigger SCIV's and SCV's into AUDIBLE distress full range with Rock music!!!!(not even as demanding as DD/dts soundtracks!). If you doubt this, just come over to my house and I'll show you! Also, I know that the SCIII's drivers are EVEN EASIER to blow if you're not careful. I can attest to it from experience, trust me.
Yes, the Dunlavy's handle power pretty well, largely due to the construction of design, and dual drivers helping to audibly cancel out distortion differences between themselves. That's why this design sounds so "fast" and "acccurate sounding" largely(that and coherent point source, time alignement, etc).
And infact, my experience has been that the vast majority of speakers(and the SCIII"s aren't full range...just a big monitor really) is that they can't handle full range DD/DTS full range anyway. THX speaker systems recommend 80hz crossover points for a reason...it works! Unless you're running powered speakers or something, passive designs should assist the help of an active bass woofer(s) bellow 80hz usually, which makes something like the SCIII sound WAY MORE DYNAMIC, POWERFUL, CONTROLED, and EFFORTLESS!
Yes!...I would indeed cross overy your SCIII's at 80hz, and place them well with the sub filling in the bottom.
like anthing else however, you should tinker for best results. Maybe you're pre/pro crosses over at different points, and it's worth a try. But, Still, an easy sollution is always the 80hz crossover if you can get both the sub and mains coupled to the room at that frequency well...then you're doing very well indeed! Even though the SCIII's are adept performers down to 40hz on their own(as are many many other speakers), for the much less demanding music material largely, you will be coming to a point of dimminishing potential REALLLLLLL quick with what movies are now pumping out bellow 80hz! And besides, you're still using all of the SCIII's 6" woofers when crossing em at 80hz, and you'll lose none of the speed and impact in that critical 63hz-100hz reigion! Yes, you can argue that you'll be losing(potentially...if you can't set up your subs properly) potential bass articulation capabilities between 40hz and 80hz with the SCIII's cut off at 80hz(slopping down 10db at 60hz or so). But the trade off benefit is WAYYY WORTH IT!
I can't tell you HOW MANY TIMES I've heard audiphiles on THIS AUDIOGON forum say they are BLOWING DRIVERS in their much large full range speakers with some of the DD/DTS DVD's out there now!...and they aren't even listening loud!
So, you tell me you think you can do full range properly with 6" monitor drivers for bass out of the SCIII's!?!...I think not.
Maybe if you're going to listen at very very low levels all the time, you might not sweat it any. Still, the dynamic ability will be limited that way.
But, if you do want to try doing full range with the SCIII's(or any passive speaker) for movies, be prepared to possibly replace a driver if you try anything close to THX levels! 6" bass drivers CANNOT handle 20hz dynamic information at higher levels...so be careful.
If you doubt, maybe you can "poll" all people who own/owned SCIII's and ask em if they ever replaced drivers on em?...it couldn't hurt.
Still, the SCIII is a nice speaker, and excellent for HT IMO if you set it up right, and don't ask too much demanding bass from the bottom end...CAREFUL!