How good your renders are doesn't simply depend on the software you use; it depends on how good a craftsman you are. Learn to use Carrara to its limits and you'll be able to turn out renders that look as good as most of the best out there. There are probably a lot of people who shell out a lot of money for 'the best' but who don't put in the time (or haven't the talent) to get a good result. And it's worth remembering that when you look at a render you've not really any idea how much postwork was used, whether render passes were used to fake effects, compositing or other image manipulation techniques employed. It's all legitimate (it's all a 'fake' anyway) but it makes it very difficult to assess particular software. If you're REALLY keen to learn about rendering, I recommend 'digital Lighting & Rendering' by Jeremy Birn, published by New Riders. And by the way, AGrooves does NOT do rendertime displacement, it creates geometry before render.