A few comments for the record:
The current retail price of the DEQX is $3795 (not $2700). Add four additional channels of good amplification and you have a serious investment.
Does it sound better than the passive? Some who have heard both report hearing an improvement in imaging and sound staging. But it is not necessarily what I would call a dramatic improvement.
Is it more versatile? Yes. You can't tailor bass response to your room with a passive crossover.
Is it worth it? It is your money. I can't make that judgement. The cost of entry is about double a passive crossover and the improvement is incremental. If you want the best speaker I currently produce, the HT3a's are it. But you be the judge.
I do not recommend this. While there may be advantages and you could certainly use a tube amp for the midrange/tweeter and a good SS amp for the woofer, it would be difficult to get the levels correct without measurement equipment. The average enthusiast would be better served with a good amp and just let Dennis' crossover do the work for you. It is about as good as it gets - no muss, no fuss.
Some people say that outboard crossovers are the only way to go. The crossover components are not subjected to vibrations internal to the cabinet. I don't think I would go quite that far.
Others don't like the idea of separate boxes sitting next to your speakers.
But if you want to future-proof and don't like the idea of switches in the signal path, outboard crossovers are the way to go. Use the passive crossover now and simply disconnect them in the future if you go active. The only downside is the cost of the outboard enclosures (which is about the same or even less than the switches).
If you want the best that current technology will allow, an active set-up with DEQX is at the cutting edge. But IMO, the HT3's with passive crossovers perform so well, most people would be more than pleased with this set-up if they never moved beyond it.
Personally, if the passive HT3's were the only speaker I had, I wouldn't spend a single moment worrying about it. I'd just enjoy the music. (Of course, I will admit I am rather biased where the HT3's are concerned. I love this design and even though I have been building them for a while now, they continue to amaze me.)