series/parralel 3 sub wiring

Use any mono amplifier.  RMS output of the amp should be anywhere close to the combined "continuous power handling" specs of the three subs.  For example, if each sub can handle 250 watts continuously, the amplifier should be able to output anywhere up to 1000 watts (spec'd at 2 ohms).  Above that (in real power), you should be very careful not to exceed the subs' capacity to handle the heat.  The type and size of their enclosures will have a lot to do with this.

(re  your sig):  In other words, don't take it to 11.

1.  Unless you are building an SPL competition car, I never think a BP enclosure is the way to go.  Build a ported enclosure.

2.  I have no idea if that amp will actually perform anywhere near its rated specs, but as long as you set the gain properly you can literally use any amplifier with any speakers.

3.  Upgrade the big 3, and install the highest capacity alternator you can afford that will fit your vehicle.  Extra batteries are not necessary unless you plan to listen to the system for extended periods with the engine off.

Have fun!

I'm continually amazed at the specs these car audio makers come up with.  Here is an earlier thread:  https://www.the12volt.com/installbay/forum_posts.asp?tid=88330

The subs are far generously overrated as well, but...that being said, it would be fine to pair them up as you plan.  Keep the subs wired to the 3 ohm impedance as illustrated in the previous post.

Plan to work on making a ported enclosure.  Tune to 40 Hz.  Make each chamber separate, with its own port (advised, but not mandatory).  Specs for loading into WinISD or other software:  http://www.poweracoustik.com/pa2006/product_AUDIO_wof_mofo.htm  unless you have something different that came along with the subs.

There are three distinct steps you must do.  1.  Plan and build the enclosure(s), as well as work out all details of amplifier wiring.  2.  Get a lot of damping and adhere it to the sheet metal of the vehicle while it is being prepared for the install.  3.  Use the Big 3 sticky as a guide and go carefully over the existing wiring in the engine bay.  You may need to add as little as an additional, larger gauge ground wire from battery to chassis.  Or, you may need to look into upgrading the alternator and adding associated wiring at larger gauge.  But damp the metal and build the system first....don't bite off too many chunks at once.

The subs really do require a vented box, but you should avoid tuning too low for these.  That's why 40 Hz is recommended by the maker.  Ensure that you have a subsonic filter on the amp, set to ~35 Hz.

For reading about SPL comps on this forum, google jeffchilcott in the search window https://www.the12volt.com/

As you spend more time browsing the info found here, you will get a better sense on how to set your system up for comps.  You have to start somewhere, so just do it.