I got a 200 amp box, looking for best standy generator for the job

Im looking at about 100 amps dedicated to 12 lights on a 60 amp timer, 30 amps for ac/heater and the remaining for minor stuff. But I also need to power the home which has 3-4 acs during summer. If anyones done this before that would be great. Im looking at GENERAC Guardian 5875 20KW Standby Generator right now with a automatic transfer switch together im looking at 6,000 ish.

$5200 incl. shipping. Just looked at these for my mom's house

http://www.amazon.com/Generac-5875-Air-Cooled-Generator-Compliant/dp/B003IT76F2/ref=sr_1_1?ie=UTF8&qid=1320904312&sr=8-1

looks good should have said i got 12 1K hps and 30 amps on ac with rest of house im thinking we will need next model up. Also I got the actual house I got to power, my electrician said I got to write everything down amp wise for start up and well go from there. Apparently having a generator is a luxury item but I look at it as a necessity. Anyone rocking that kind of power fill me, otherwise I think I might buy extra stuff, definetly have to get the auto transfer switch but I want to know if I should buy the 10 minute delay starts or if the power never actually stops.

There was mention of the liquid cooled generacs just this week... I am about to buy a 27KW generac quiet whatever it is called...