It would 175W RMS into the speaker itself. I guess if you REALLy want to get techinal you would get 87.5W RMS to each coil, but that is really irrelevant as DVC just provides wiring options, as the SVC model of your sub is going to be just as powerful.
yeah tyler is wrong im pretty sure. if you wire a dvc 4 ohm in parallel, the you will get a 2 ohm load. therefore you will get 350 watts split between the two voice coils. you are right with the diagram.
Uh, let's try this. For example in a normal situation, 1 15" sub would be more efficient than 2 12" subs. Yes, that is true. However, if you go buy 4 12's most likely that will be more efficient due to cone area and so on. Really, multiple woofer systems are more efficient as you have more voice coil to work with rather than a couple of 2"-3" voice coils. I.e.: My dad's home stereo has a total of 24 1" voice coil woofers in it. That will in the end be much more efficient than my 2 Cerwin Vega V-15F's with 2 2" voice coils. They will probably be somewhat equal in loudness, but if you want to consider overall sq with SPL, multiple smaller cones acting as one ginormous cone is much more efficient and is less work on the speaker by far. Just depends if you have the money to waste on an 18" or quite a few 12's. If you have the room for an 18", most likely you have the room for a lot of 12's, and should do that. Smaller cones also are not as sloppy and are more accurate. But hey, people on here seem to think I don't know anything, so go on believing what you want...
Can be is the key word. Kicker's SoloX 18" sub for example, I heard it at an audio shop once, and IMO it sounded like garbage compared to even their smaller Solobarics, where those sounded awful compared to the Comps. I just seems that it would make more sense to want SPL and SQ. So why not go with a lot of really good 12's instead of one massive 18"?