Wow, that's a great combination. I have setup the same one in our store before and it was awesome. I would recommend at least 16 AWG wire, if you have 14 or 11 that would be better but not necessary (if you choose monster that's up to you, non-monster wire in the larger gauges may be difficult to come across). In terms of installation, what do you mean? You just cut the speaker wire and hook it up.
On the Onkyo I would play with the equalizer for the speakers, pumping up whatever frequency is close to 100Hz by a few dB on the EQ (+2 maybe). If your speakers are not equal in distance to your listening position you can adjust the delays (speaker distance) and volume level of each speaker to your liking. I might also turn up the bass at the 63Hz level on the woofer (or whatever the lowest is on your Onkyo's EQ) if you care about bass. That dual-firing woofer setup is capable of way more than the manufacturer says.
I guess you could say that the best way to find out the best settings is to tweak it to your specific room/liking. If you are going to be using it for music find a reference song (one that you KNOW what it supposed to sound like) and adjust your speakers based on that. Personally, I use "Crazy on You by Heart" as one of my reference songs.
Finally I bought Onkyo 805 receiver for my KEF KHT-3005 5.1 speaker system. Can you guys help me to clarify couple of question?
1. I want to install it my self, is there any link where can I get help how to install?
2. What wire i should use to connect the receiver to speaker for best sound?
3. Any other tips for installation and get best sound out of these two combinations.
Thanks in Advance