High efficiency speakers

Are you talking about high frequency drivers, or subs?  If the former, HLCD's.  If the latter, Phoenix Gold Cyclone.

But I will let you know one thing on the subs.  Hoffmans Iron Law states that you can have two of the three, but never all three of the following; high output, small enclosure, or high efficiency.  So if you want high output and high efficiency, expect the enclosure size required to be very large.  This will also be true for mids if you decide to put them in sealed kick pannels.

I was talkin about drivers.  At the moment, I've got Pioneer coaxes all around.  I'm planning on adding a 4 channel amp and going to 6.5" components all around on my next revamp.

How does a sensitivity of 106 dB sound?  That is the sensitivity of HLCD's I mentioned earlier.  Here's some links to a couple manufacturers:

http://www.illusionaudio.com/illusion/Driversx.html

http://www.imagedynamicsusa.com/website/products/horns.html

The Pioneer coaxes sounded great - for about a year.  I'm revamping because now they rattle (guess they're blown, but I've only been pushing them with the HU at relatively low volumes).

Just make sure you are not driving your amp into clipping.  A head unit with 22wpc can be easily driven into clipping and that can fry a voice coil, especially of a tweeter.  If your speakers are "rattling," however, I would suspect a woofer cone or surround is gone.  Pioneer = generally cheap construction, so I am not surprised and it probably had nothing to do with your amp.

I don't know the HLCDs, but I really like the sound of both the Kappa and the Hex.  Diamond has a much better high end with smoother sounding tweeter, and the Infinity has better low to mid bass.  You can't go wrong with either, so get the ones that sound the best to your ears since you are the one who will have to live with them.