what do I do about 40 foot rear cable lengths?

I am setting up my home theater and I need some advice.
I am using a denon 5803 that has not arrived yet, so I may have to use my yamaha rx3300 until it arrives. I will be using my infinity IL-60's for the front and rears and two beta 360's for the center channel. I plan to use the unused rear surround 170 watt channels via rca. hopefully the receiver has a surround back rca output that I will send back into the unit's center channel and then run the new wire to the other center channel. anyway my concern is that I have two 40 plus foot cables to run for the rears. Im not sure if there is a way during setting up the receiver to account for the long distance.
any thoughts. also I am going to try the hd-14 method of wiring the speakers.
Frank, that really shouldn't be a problem, especially for surround speakers. While the ideal is to limit cable length, you'd really only ever notice in an extremely resolving sitution (IOW main speakers in a really high-end rig). Most surround information is not "high fidelity" relatively speaking.

IMHO, the practical liability of longer lengths is that they can exhibit antenna-like behavior so you should avoid running these parallel to any house current or other wiring. If your runs will intersect with any high voltage (house current) wire, try to cross perpendicularly with a couple inches of separation if possible.

The only other thing to keep in mind is that you will need to calibrate some delay, which depends on where you sit in relation to the various speakers. For example, if you sit closer to the rears, then the sound from them will arrive prematurely (relative to the rest of the speakers) so you'd add delay to the rears to get everything in synch. Your setup guide will tell you all about this (if you're not already familiar) and the new receiver may even have autocalibration.

Hope this helps!