Either the 60D or the 650D are good updates for the 550D. I started out with a 550D and after an inheritance I decided to upgrade and have finished up with a 5D3 and a 60D whils I gave the wife the 550D. Then when the 650D came out I bought one for the wife and eventually sold off the 550D.
The 60D, for me anyway, gets the vote as it has better ergonomics and is layed out more like the 5D3. The 650D has very similar features in a lot of ways, but it has better ISO handling and the touchscreen is excellent. If I hadn't got another body with the different styling I would of gone for a 650D in a heart beat.
Mystery57, if you are anywhere near the Lincoln area and want to come and have a look and play with the 60D and the 650D just drop me a PM and we can make an arrangement.