I think "Turn Left at Orion" is a great handbook which will help you get an appreciation of what you are looking for. There is a companion web site, which has sketches of many of the main targets, including the Helix Nebula, which has sketches for an 8" SCT and a 4" Newt:
http://www.cambridge.org/features/tu...a_NGC_7293.htm
The sketches are generally negatives (dark stars on a white background) as this is generally easier to interpret. The sketches for an 8" scope typically assume you have good viewing conditions; if you suffer from a bit of light pollution, the 4" views might be more representative of what you'll see at first glance, especially if you haven't got fully dark-adapted vision etc.
I have inverted the sketches for the 8" and 4" views and attached them - as you can see, the Helix probably won't "knock your socks off" unless you have reasonably good viewing conditions.