Like everything in this world, it's a trade-off. And, depending on your situation, they could be great or not-so-great. I have a pair of MG-12's with a powered sub with an active cross-over as these are a little shy on bass. (This is less the case as one moves up the line into the 1.6's, 3.6's and 20.1's.) I'll echo the sentiment that there is a fairly narrow sweet-spot on the 12's, although once again, moving up the line will minimize this weakness. And yes, they do need power- I had a 100 wpc(at 8 ohms)Counterpoint amp which had a tough time getting to a little more than moderate volume, even WITH the active x-overed powered sub, and quickly moved to the 220 wpc Counterpoint amp. (With all due respect to others, my opinion is that the bare minmum would be a 120 to 150 wpc of QUALITY amp for the 12's and 1.6's, and no less than 200 for the 3.6's.) Lastly, they do need space and are somewhat room and placement dependant and, with respect to size, I did find that the 12's are alot less obtrusive than the larger models.
If these negatives haven't run you off yet, I'd say you need to get a pair of Maggies. They are a great speaker for the dough!
BTW- Maggies are very revealing speakers- the HF harshness that some refer to is quite likely to be caused by an amp that doesn't work well with the Maggies.
Regards
Jim