generally speaking, speaker power ratings are thermal ratings. That is, it's how much power they will take before the voice coil melts. Generally speaking, with woofers, most of what I read suggests that the device will cease to be linear (start compressing) and possibly start making ugly noises by somewhere around 1/2 of the thermal rating. AFAIK, peak ratings are essentially meaningless. I think they are often simply the instanteneous power at the top of a sine wave at the max RMS level, which means they're a different, less informative. way of saying the same thing.
How much power you need depends on how loudly you want to play (and the not little issues of box design, especially for subs). You need enough power to get them as loud as you want them. That's what a designer would recommend. The speakers do not NEED 300 watts each to make sound. In fact, in a normal room, if you aren't using a lot of EQ to boost extension, you can achieve very loud levels (certainly over 100 dB, with well under 50 watts. Depends on the sensitivity of the speaker (and whether that sensitivity rating is relevant at subwoofer frequencies or cops out by using a psuedo-industry standard 1 KHz tone . . . . Just because they theoretically can see 600 watts without immediately failing does not mean you ever will need to give them that much power. Those Infinities are 93 dB at 2 watts. So 2 of them at 4 watts (assuming they are co-located) would be about 98 dB. So 40 watts would yield 108 dB, and 80 watts about 111 dB and 160 watts about 114 dB. Movie reference for the LFE channel is 115 dB. So ignoring added burden from bass management, it takes something like 200 watts to hit 115 dB. Theoretically, anechoically. If you put the sub on the ground or on the floor, you gain 6 dB from dividing the space in half. If you put it on the floor against a wall, you gain another theoretical 6 dB 9but walls and non-concrete floors will have some loss . . .) Then there are losses as you get farther from the sub (6 dB per doubling of distance (from one meter) anechoically, very difficult to predict inside rooms where pressurization starts to control SPL rather than wave propogation at subwoofer frequencies).
The most important thing, probably, is to be sure your amp is rated to 2 ohms under the conditions you will use it. For example, lots of pro amps are rated to 2 ohms, and lots can be bridged to increase power, running them as mono amps. But in bridged mode, a 4 ohm load looks like a 2 ohm load to the amp, and a 2 ohm load looks like a 1 ohm load. If you push the amp hard with impedances below it's rating, you're likely to generate a lot of distortion, followed by icky smells and smoke as the amp dies.