I would consider it pretty important for recovery after your cycle, if you want to keep some of the gains. You didn't say how long hte cycle will be, but even at the moderate dose of 500mg/wk, your body will shut down its own natural testosterone production in just a few weeks. Your balls will start to shrink because the body thinks they are not needed. After you end your cycle, with shrunken testicles, it will take a lot longer to restore natural testosterone production. This would cause you to lose much of the gains from your cycle, as you need natural testosterone to hold on or protect muscle mass. Using HCG after your cycle will quickly regrow your balls (the stuff is like magic) and let you restore nat testosterone quickly. You should keep much of the muscle you gained more easily.
There are tons of posts on PCT (post-cycle therapy) on this board. I encourage you to search and read.
Here are a couple links for you:
http://www.elitefitness.com/forum/showthread.php?t=327879&highlight=radar's+sticky
http://www.bodybuilding.com/fun/cathcg.htm
http://freakzonline.com/forums/printthread.php?t=3330