I am using the HDP-3 Deqx. I use it as an active crossover for my 3-way speakers. I removed the passive crossovers from my speakers and installed 3 sets of binding posts, 1 each for woofers, mids, and tweets, direct connection from the posts to the drivers. I also use the speaker correction functions, including correction of the response delay of the different drivers, and I also use the room correction function. I do not use it for a preamp as my Steelhead handles that, and I do not use the deqx as a dac - just as a smart crossover and room correction device.
I changed my VMPS RM40 speakers to active tri-amp some 5 years ago or more, originally using an active crossover from David White of the now-defunct White Noise Audio. The improvement was enormous and I will never allow passive crossover components into any of my speakers again! Moving from the White Noise straight analog crossover (of excellent design) to the digital crossover and other DSP solutions of the DEQX was another giant step forward.
Re your problem with your computer recognizing the deqx, I also use Win 7 and have no problems in that area. I do recall some discussion about drivers on the Deqx beta users group, one of the yahoo groups. That group does not seem to be active right now but the deqx Website might have more info. I seem to recall that new drivers were needed for 64-bit Win 7, which I have, and they work fine for me. I am using DEQX 2.70; if you need it, it is available on the Deqx site
www.deqx.com/upgrades.php or you could PM me. It might have the drivers embedded. It has been a year or two since I installed it on my computer and I do not recall all the details, except that the install went smoothly but definitely required a driver package. I seem to recall that the 64-bit driver package was a self-extracting installation done first, and then the 2.70 package was installed, but I might misremember that.
Good luck - it is well worth the effort.