Agreed with the above. The Hawthorne PSI is a brilliant way to start because you dont have to mess with active crossovers, which can be an expensive nightmare, and the passive crossover is already provided. Plus they're readily available new or used.
All you need to do to take it to the next level is ditch the 6.8uF Crosscaps for something a bit more upmarket. It really makes a huge difference and doesnt need to be terribly expensive either. I used Mundorf MCap Supremes. A big upgrade and brings the best out of a not especially expensive compression driver. For the few dollars they cost, I'd upgrade the resistors too, just for fits and giggles.
The advantage of the bigger driver is better presence over smaller drivers. After doing the above, you can play with making the tweeter dipole (havent opened them up in the back yet, but intend to). Plus, you can mess around with other compression drivers without needing to do too much with the crossover. Like upgrading to Radians (havent yet but might).
And for those who reckon OBs dont do bass, they really can. You just need to move a lot of air. So another set of drivers is really needed (or two). I use another set of 15s in H-baffles and also an OB cylinder sub. I don't want for bass impact, for sure.
What's particularly attractive about the bass they do do is not its tunefulness (which is great) and nor that you can't hear the box (because there isn't one, which is even greater) but the fact that the system doesn't 'load' the rest of the house which just annoys everyone else.
What you spend on extra drivers, you save on not having to treat the room because OB doesnt interact with side walls nearly as much.
