Dunlavy SC IV Speaker- Any Good???

I wouldn't wait for a pair of IV-As to show up.  They were tweaked from the IVs to add a little more bass extension, bit I don't think it's necessary.  If you want more bass extension, wait for a pair of SC-Vs.

The Duntech equivalent of the SC-IVs is the Crown Prince/Princess, which I owned for many years.  As pointed out above, John Dunlavy designed the Duntech line (I think they now call it the Classic line) as well as his own company, which he formed after leaving Duntech.  My dealer in NJ was friends with John and one of the first dealers to carry the line, so I heard all of their speakers for many years.  My brother came to visit and wound up buying a pair of the SC-Is which he still uses today.

Your 14x15 room might just be big enough, but I'd want to make sure I could sit 10 feet away, as I mentioned above.  The Dunlavys are sealed box speakers, so they can actually be placed a little closer to the back wall than some other designs, though you might lose some soundstage depth.  You can toe them in quite a bit, if you need to put them on a long wall (as Dunlavy always suggested). 

As for Robert Deutsch, he is good at his work.

Excellent speakers, a classic design.  Amazing imaging, maybe not as transparent as the best in that area, but well-balanced tonally and excellent dynamics.  You need a large room for them to sound their best and should sit at least 10 feet from them for the drivers to integrate.  They like power, and sound really good with tubes (I have heard them with ARC, VAC and VTL), though fine with solid state as well.  If I had a room large enough for them, I would strongly consider them, even though they're no longer in production.

As to your question about power, I think Dunlavy suggested 100 watts per channel.  My recollection is that the Dunlavys were about 90db efficient, and a nominal 4 ohm load.  For my Duntech Princesses, a similar load, I used a Krell KSA 80 (100 watts pure class A), ARC M300 (300 watts pentode) and then Classic 150 monoblocks (130 watts triode) and Jadis JA80 monoblocks (60 watts), and also used a Sonogy Black Knight (200 watts per channel) and Concept 60 (60 watts per channel) solid state amps  The JA80s were weak in the deep bass but a wonderful midrange and easily drove the speakers; the higher powered amps did a better job controlling the bass and were a little more dynamic, though at the volumes I listened there wasn't that much of a difference.  I heard the SC-IVs with, among others, VTL amps (about 120 Watts) and a VAC Renaissance 30-30, and the VACs were surprisingly good, again a little weaker in the deep bass.  I think I saw you have a lower-powered Pass amp, but if it's Class A it might be able to do the job. 

My recollection is that the speakers did well at lower volumes, but I'd say they did open up a bit at higher volume levels.  Perhaps our current owners can address that question.