Having owned the Druids and Defs, and now Def. Pro's, I suppose I'm unusually prepared to answer this question. Yet, I don't think it's an easy question.
Some listeners find the presence band of the Definitions to be a little hot. It measured flat in my room, but even so, with aggressive music I found equalizing that band down a few db was preferable to me for hard rock and music that "lives" in that band. Mellower fare and just about everything else is great without eq. Bass response of the Def's is wonderful. It measured and sounded flat in my room to 30 hz and dropped from there. Despite the claimed extension to 16 hz, I was not able to meaningfully equalize the stock Def's to have meaningful output at 20 hz. I think my room is a big bass vacuum. In that room, bass was strong, quick, tuneful, and INTEGRATED. It was amazingly coherent, and the handoff between the front and back drivers was seamless. But, it wasn't a kick in the chest.
The Druids are naturally down a couple of db (I've heard) through the presence band and are less likely to require some type of equalization. These speakers are incredibly nimble and tuneful and the bass is good down to the rated 40 hz. That said, it is not particularly impactful. I would imagine a Velodyne sub (or two) would be tremendously impactful. This might cause integration problems. In fact, there's no guarantee they could ever be completely integrated in your room. If you want to rock the house, that wouldn't matter too much and this might be the better combination. Also, if you can't sit at least 10 feet from the speakers, you might go this direction.
Consider the Def. Pro's. They're not much more money, and you can get complete eq. control. I'm using a TacT 2.2x, which allows complete control over XO properties and frequency response. I have a wild idea that this could be used as a dipole in the bass region in the right room, but alas, my room is not configured to let me do it. Zu actually uses a pro driver for the rears that have 4x the output power at 20 hz vs. the stock drivers. Last weekend, I literally had a door rattling in the doorjamb with infrasonics that I could barely hear.
The only downside to the Pro's is the commitment. You'll need two amps, an equalizer for at least the subs, and sufficient patience to dial it all in. But, I think the result could be tuned for ANY audiophile's wet dream. Me? I've got a Yamamoto A-08s 45 amp ordered for the front array and an Adcom 555 200wpc SS amp driving the rears. Can you say magic midrange AND over-the-top bass performance?
You definitely should get Phil's take (213cobra). He currently owns Druids and Definitions, both with outstanding amplification. Good luck in your decisionmaking, I don't think there's a bad choice.
Mike
