Check this post out
That little device would probably help, but reading the spec it has a 500 ohm impedance input and optimal output at 8 ohm impedance, its kind of backwards for your application, I think.
You are taking a 32 ohm impedance input (output from your iPod), going into the 500 ohm booster's input. The output from the booster (8 ohm), going into the 600-1000 ohm impedance intercom aux input. You really want the opposite. It will do something (may be), because the amplifier might makes up for the miss-match inefficiency. If the device has a low power preamp, it will not help. You can buy it, try it, use it, keep it or return it, if it does not work.
iPod's output only 0.75v. Line-out audio (non-amplified) are 2v to 5v on most audio, meaning the iPod is only made to drive tiny ear buds. When you have to crank any amp, including the iPod, quality goes down. Lots of built-in inefficiency (mis-match), plus a low output amp, means you have low volume and/or distortion.
May I suggest a passive, easier and cheaper way, that might fill the bill. I just wrote about this in the link below. The issue is impedance mis-match. The iPod is 32 ohms and your intercom is 600-1000 ohms. A mini audio matching transformer, matches the impedance (close enough). This boosts volume without adding any preamp. You can make your own or buy it commercially for $35. (SEE LINK BELOW) Some low end intercoms might still benefit from both matching transformer and a pre-amp, especially with an iPod.
http://www.vansairforce.com/community/showthread.php?p=196367#post196367
If you still want an pre-amp, a better mouse trap you might want to check out is this link. You can make one or buy it commercially.
http://www.minidisc.org/headbanger.html
Your PMA 8000 is stereo I assume. The PMA 8000 is top end unit and no doubt has a preamp in the aux input, so I think you will get more mileage out of the impedance matching. Some intercoms do suffer from not only impedance issues but a lack of pre-amplification. Still low output voltages from little devices (like iPods) is an issue. The miss-match just makes it worse. Call PS engineering and ask them.
Here is a TIP: Using the iPod's LINE OUT instead of the headphone jack gives better sound quality. You will need a preamp using the LINE OUT, which are not amplified at all. The headphone jack audio is running through the little internal amp, which lowers the sound quality. The line-out requires a car charger cable with LINE OUT audio.
LINK Why did Apple not make a more powerful headphone amp? Size and power consumption no doubt.
Make your own preamp and mount it permanently?
Preamp electronic hobby kits, mono or stereo. I picked a few, put them in order of what looked like the best match for the iPod to intercom application.
http://www.electronickits.com/kit/complete/ampl/ck704.htm
http://store.qkits.com/moreinfo.cfm/QK87
http://www.hobbytron.com/CK122.html
http://www.hobbytron.com/Preamp2WAmplifierMicrophonePreAmpFullyAssembled.html
http://www.hobbytron.com/vk2572.html
(A full 1 watt makes up for the sin of impedance miss-match. We are not talking hi-fi here, just getting acceptable volume. There are many suppliers of electronic hobby kits. Some kits above are more suited for battery operation 3v-9v, others work out the box on 12v-15v, suited for powering by the plane directly. You can make a little power supply voltage regulator if needed to may any of the above work off of ships power.)
