Having own numerous monkey coffins (box speakers) my first foray into OB was with Accoustat 2 + 2s. I had both the interfaces and the servos, to which overtime I did some upgrades. The servos were great, but too many times I experienced cherry red tubes. Long after selling them someone figured out how stabilize the servos. Eventually, I bought a pair of 3.5Rs but by themselves their sound got lost in my big room, so I added 2 SVS powered subs, but couldn't get them to blend seamlessly. I then tried multichannel W4S amp, then replacing the OEM XO with active, which was getting closer, but the cheap Behringers and DBXs kept blowing up. A couple years ago I sold them and bought Emerald Physics KCIIs with $1000 worth of upgrades, but they did not match up with my subs. About 6 months ago I got a pair of EP 3.4s, which are magical if your room isn't as big as mine, but my subs match up pretty well. The 3.4s are ~ 99dB efficient (no complex load here) with a concentric polyester tweeter, and sound amazing. A big benefit is they are only 40" tall. And since the line was discontinued you can find them damn cheap
hth
hth