I'm a fan of active speakers. About 20 years ago compared Paradigm Studio 20 v.2 ($800/pair, 2-way monitors) versus Paradigm Active 20 ($1600/pair, same drivers/cabinet with the power amps attached). It was no contest. The Active 20s were way more dynamic, flatter frequency response, improved imaging, and gobsmackingly deep/full bass and compared favorably to the $2200/pair Paradigm 100 v.2 floor standing speakers. Passersby couldn't believe the disconnect between what they heard and saw.
Don't make the mistake of confusing active with powered speakers. Active designs use a low voltage signal input (like RCA) to more sophisticated crossover which feeds one channel of power amplification to each driver for superior design and performance. Powered (Audioengine is one example) are simply passive designs with the power amp built into the speaker. And realize that being active doesn't mean that the crossover/amps have to be built into the cabinet (but it is cheaper). Bryston is an example of the this external approach.
Studio professionals have used them for decades. Active monitors are often cheaper and much smaller than comparably performing passives even without including the cost of speaker cables and power amp. This is due in part to not spending money on larger cabinets, extra shipping costs, and fancy veneers. A good example is the JBL 305 Mk2 ($300/pair, can be used on desktop or to fill a medium sized room, it provides a very satisfying sound).
I've heard the JBL 305 Mk2 in my room along with it's big/big brother, the JBL 708P ($4000/pair, large monitors) which I owned for a year. The 708P's were overall the best speaker I've ever heard/owned, meaning that it did all things very well without being gastly expensive, or huge and didn't overload the room while remaining dynamic and detailed. Have also owned Dynaudio BM5 Mk3, very comparable to the original JBL 305 (which I had here for a week).
Most active speakers are designed for the studio, so use XLR (balanced) versus RCA inputs. But a new breed of actives are being introduced that accept wireless (digital) input. The Elac Navis ERB-51 in fact accept either wired analog (so you can input phono/tape or use your higher resolution digital sources with the DAC of your choice) or wireless (where the speaker uses it's own DAC). Note also that many active speakers convert analog input to digital then back to analog, again with their own DAC.
Recommended analog active monitors (that don't have an on board DAC) include Adam (various models), Dynaudio BM5 Mk3, Genelec 8030C/8040B/8050B, JBL 305 Mk2, and Neumann KH120. Recommended actives with DAC include the aforementioned Elac, various Genelec monitors (which can get expensive), and JBL 705P/708P.
