I got a Bose system with individual amps located next to speakers , and speakers measure DC Resistance of 1.2 ohm , which the nominal IMPEDANCE (different) is probably 1.5 or 1.6 ohm - Bose uses VERY low impedances for these setups . The amps are typically H-bridge MosFet , fed " high level " and extremely low Z (impedance) out .
In Crutchfield , I believe FOCAL makes some stuff to go right in Nissans , the right physical fit AND a 2 ohm impedance . As VStar says lower output using BOSE 1.6 ohm amps with ANY 4 ohm speaker gonna sound like a little light at the end of a tunnel , lose lot of dynamic range to the ear too is what I hear many say putting 4 ohm speakers in Bose type system. (decibel ratings aside)
Now I got 4 Bose round ,like 4" to 5 1/2 " @ 1.1DC Resistance ohms that came from buying the 4 slave amps off ebay , my speakers were different AND OK so I put just the amps in , with " Beefed-up " the heat sinks in the J30.Gets 120 F in AZ !!
If your interested ( round Bose speakers ,have 4) I can go to storage get photo ,and verify size ,depth , and DC resistance ohm and sell to you cheap
p.s. FOCALs I mentioned = $$$ 300+ for just two
