007,
Yes, the Def Tech house sound is more oriented towards home theater use. The Mythos 4 are really a very complicated based on their performance (3-way, 5 drivers, plus 2 passive radiators). I prefer simpler designs that use better and far fewer components.
It seems like you're after a more mature sound now. Low/mid volume and smoothness align nicely with capturing the tonal qualities of voice and instruments does. Dynamics can be microphonic (small) or microphonic (large) instantaneous volume swings, so on a smaller scale dynamics can be worked into the mix.
I enjoy a rich sound too. Unfortunately the general trend in audio has been towards a more spritely, tight sound (like the IDA-16). Going with a larger bass/midrange driver (15 - 20 cm diameter) helps produce a full mid-bass presentation to achieve a full bodied sound. I hesitate to use the word "warm" because many associate it with colored, slow, thick, and dull sound. Many of today's tweeters (ribbons, metal domes) seem to be oriented towards satisfying older ears (that struggle to hear higher frequencies) and make for a less rich sound.
If you are satisfied with how loud your old system was (with the KEF subwoofer), I'd recommend investing your budget into a quality pair of stand-mounted 2-way monitors (versus fancy cabinetry). Speakers like the Philharmonitors that Michael listed, Ascend Acoustics Serra, Fritz monitors, and LSA-1 (look up Underwoodhifi.com) should be on your short list (if you don't have children/pets that can knock them over).
Many companies, like Salk (their sound is largely after the Def Tech genre) or Sonus Faber (they have a richer more musical sound), emphasize the expensive cabinetry. Is that what you want to pay for?
But as always audition at home. You are the only expert who matters when it comes to your system in your room.
The IDA-16 is a very fine piece, I recommend you match it to a very good speaker.