The subs you mentioned are very different in the way they were created resistance wise. The JL W6s have dual 6 ohm voice coils. Your TOTAL ohm load depends on three things: The number of speakers, the number of voice coils, and the ohm resistance per voice coil.
Both subs you mentioned have dual voice coils, but the Punch's are 4 ohms each, and the JLs are 6 ohms each. Therefore, the ways that they are configured for different ohm loads are different.
If you're getting 3 JLW6s, and want a total bridged load of 4 ohms, then you're wiring each of the voice coils (per sub) in series so that each sub now has a load of 12 ohms total. Then you wire all the subs up in parallel for a total of 4 ohms. This can ONLY be done with 3 of these subs, and this method ONLY works for the JLW6s.
The Punches have two 4 ohm voice coils each. They are not quite made for triple sub applications, unless your amp can go down to 2.33 ohms BRIDGED, which is difficult for the common amp. These subs are made to be used in pairs or fours with most amps. With this type of sub, I'd recommend either two or four, not three for 4 ohm subs. If you want a 2 ohm load, then wire each of the voice coils (per sub) in parallel, and then you'll have each sub running at 2 ohms. Then just wire one sub up to each channel. If you want to BRIDGE your amp, then wire your voice coils up (per sub) in series, so that each sub is at 8 ohms, and the wire each sub up in parallel to the bridged amp, and you'll get 4 ohms.
Ohms is calculated by:
Wired in series: Ohm total = Ohm1 + Ohm2 + ...
Example - a sub with two 4 ohm voice coils: 4 + 4 = 8 ohms
Wired in parallel: (1/Ohm1) + (1/Ohm2) + ... = (1/Total Ohm)
Example - Punch (Dual Voice Coil) with 2 4 ohm voice coils:
(1/4) + (1/4) = 1/Ohm Total * Solve for Ohm Total
2/4 = (1/Ohm Total)
Ohm Total = 4/2
Ohm total = 2 Ohms
Try drawing out diagrams and messing around with the calculator for a bit. It's not that hard, and it's fun once you get the hang of it. Then you can mess around on paper and really see what you might want to try with different sub setups...
Good luck!
Jon
