Yes, as long as you are paying less that $120 they are the best value out there thanks to their decent displacement and sensitivity. On a strict budget, there is just not a better 15 out there for the money. Also keep in mind that PE offers $5 off coupons all the time too and these price include shipping. I paid $116 for my first one and $99 for my second.
An enclosure size of 3-4 cu ft. sealed is plenty. In fact I'm leaning toward 3 cu ft for my next build as the x-mech seems to not be much past x-max. I can bottom out a DVC easily in 3.5 cu ft w/ a signal generator and 600w, but have yet to do so with program material. With a 20hz sine wave I get about 102db at the listening position from 1 dvc. Any more and I hit a mechanical limit. PE doesn't list a spec for x-mech.
Build quality, save a few reported defects, is generally good and it's a USA made Eminence speaker. However, the parts list leans toward the inexpensive side with the stamped basket, foam surround, paper cone and 2" voice coil. So, there are better options out there if you can stretch the budget a little closer to $200ea.