Putting an aftermarket radio on stock bose speakers: This applies to any generation maxima, and #4 applies to 4th gen and up.

Your factory Bose head unit sends an unamplified audio signal to the Bose amps. So you want to replicate this as close as possible for the best sq, in theory. There are a few options:
1) You can wire it up as a normal head unit without any Bose adapters, and have a small risk of burning up the Bose amp(s).
2) You can buy the $50 PAC or Scosche adapter, such as the one here
4th gen and up: http://www.crutchfield.com/S-7pnyu0E...51&I=142C4NN03
3rd gen: http://www.crutchfield.com/S-7pnyu0E...51&I=142C4NN02
3) You can wire the deck's preouts to the wiring harness in the dash, which will send an unamplified signal to the Bose amps. You have front and rear preouts. Each of those has a left (white) and right (red). So youd plug in RCA ends to the front and rear preouts, leaving a few inches of wire for you to play with. For the front left RCA, there will be 2 single wires inside it. Wire those to white and white/black. The front right, wire those to gray and gray/black. Do the same for the rears, Rear left will be the green and green/black, and Rear right will be purple and purple/black.
4) You can buy the Metra 70-7551 for 4th gen and up, or 70-1764 for 3rd gen (which is usually hard to find locally) which will already have all of Step #3 above done for you, so you can just plug stuff in.
http://www.metraonline.com/i/METRAHANDOUT_2005.pdf
Page 25 of 36 is a pic of both the Metra 70-7551 and 70-1764.

If you need your radio installed asap, the most cost effective way is Step #3. But if you can find the 70-7551 harness, or have time to order it online, it will probably save you some headache. Those are the easiest, most cost effective methods of this installation.

Caution: If the voltage of your preouts isnt a decent amount, you might want to avoid steps 3 or 4 and go with step 2. Low voltage preouts combined with step 3 or 4 will equate to your Bose speakers not getting loud once installed.