With JL Audio, it kind of depends on what sound you're shooting for. If you're not into the brain-numbing bass, you can easily get by on W1's or W3's. The W1's are a really clean sub that will play upper bass frequencies just as well as the lower frequencies. It gives up some power handling (SPL) and ultra deep bass you would get out of the W6/W7 series, but you do save some cash not only on the subs themselves, but the amp you need to drive them. Unless you're willing to fork out the money for the W6/W7's, the W1/W3 series will make a great 'daily driver.' (pun intended)
You mention wanting the overall sound to be louder. You can easily accomplish this by using outboard amplifiers. As far as clarity, that will depend on speakers, proper amp gain settings, and crossover points. I can't tell you how many people can't properly set a gain and as a result, muddy one-note bass and tons of distortion. Few take my advice, but when setting a low pass crossover point for a sub, use a low one, like 50-60Hz and use a high pass x-over at around 80-100Hz depending on your mid-bass/range driver. 'Cabin gain' more than compensates for the missing frequency gap, as verified by RTA tests. Subs that can't cleanly produce upper bass notes (80-120Hz) ruin systems.