STS option Packages / Pricing 06-07's

Greetings all. A newbie to the STS forum, but not new to forums. I've just come from a 6 year stint of the C5 Vette. Very active member / participant / Diy'er so very familiar with the forums. Hope to contribute much here as well.

But, here is my question(s). I will by buying an 06 - 07 STS V8 in the next week or so - just trying to find the ones I like for now.

OPTIONS: How does one decipher all the differnt option packages? I drove and 07 V6 and then a 06 V8. Like night and day. V8 it will be!

Problem is how to determine differences in options. Obviously I want the NAV ACC heated/cooled seats but trying to match apples to apples isn't easy.

Can anyone tell me what to look for - which are really nice options and others just gimmicks. The voice command looks cool but does that add significantly to the cost.

The other huge issue I am seeing is the vastly different pricing on these STS's. Why would some be in the high teens / low 20's and other seemingly virtually the same car similar options and mileage be upper 20's? WHY is that?

If someone could point me in a direction to actually compare STS's apples to apples, I would have far more knowledgeable bargaining reference.

Thanks... and looking for a great time and a great ride in my STS. A lot of the Vette guys highly recommend them and a lot even use the STS as their DD and the Vette for just good/fair weather days / events/ and cruise-in /shows. (not me - I drove mine like I stole it! and loved every minute of it)

Any help would be appreciated.