The G500 or G400 are both good options. I've used the G400, and it certainly is very smooth and accurate. Its only downfall, for my needs anyways, is the lack of the middle mouse tilt feature. Most people don't like the tilt anyways, so you may prefer it. If you do like the middle button tilt, the G500 is practically the same as the G400, with a tilting middle mouse button, and one additional thumb button.