I thoroughly checked out the 520, the Jamis Aurora, the new Aurora Elite, and concluded that the Jamis was more appropriate for ME for the following reasons;
1) The Trek's head tube wasn't tall enough to bring the handlebar up high enougg without doing a lot of surgery on the stem.
2) The bar end shifters, while nice for their reliablility, positively suck for city commuting. I mostly ride atop the bars, and having to constantly reach down to shift in traffic is a complete non-starter for me.
Yes, the 520 has a better parts package than the regular Aurora, but definitely not the Elite, although the Elite is basically a cyclocross with a road triple. But the parts difference between the 520 and regular Aurora might not make as much of a difference as you might imagine. It's all good.
Like everybody has said, it's all about fit and the purpose for which you're using the bike. As a matter of fact, I'll probably do very LITTLE actual touring on my bike, but I'm looking moreso for a great ALL-PURPOSE bike, and the Aurora seems to fit the bill perfectly. I also love the cheater (interupter) brakes on the top bar in addition to the brifters. On the Jamis, I counted 6 different hand positions! And they were all comfortable. To me, that's what's important. Plus, I like the longer wheelbase advantage the Aurora has over the Aurora Elite. The Elite has a waaaay better parts package ($1250 including 10% discount) with an Ultegra/105 mix, but the gearing was higher (10/27 rear cassette), there were no interupter brakes, and the headtube was shorter (it's an 07' rebadged Aurora). Also, the 631 frame seemed to ride a little stiffly, which I didn't like.
As for fit, I subscribe to the Rivendell method; when in doubt, buy the bigger frame.
I tried both a 50 and 53cm Aurora, and I fall right in between sizes. The 50 seemed a bit small, lower to the road, with just a fraction of an inch of toe overlap without fenders. The 53, although feeling a bit stretched out, felt waay more comfortable; with a commanding view of the road (higher center of gravity though), and not even a hint of toe overlap. During the test ride, the pedaling circles just felt "right". And after shortening the Ritchie adjustable stem, and flipping it upside down, I was MUCH more comfortable, and didn't feel too stretched out. Now, all I have to do is double check the seat position to make sure my knees aren't too far forward or back.
Btw, I'm 5'6", with a 30" pant inseam, a 32" Pubic Bone Height (ala Rivendell), and have just under an inch and a half of standover clearance on the 53 Aurora...and about 2.5" clearance on the 50, which felt like too much. And if it needs reiterating, cockpit POSTION/fit is WAAAAAY more important than standover height. If you're trying to decide between two sizes, I'd recommend going larger and adjusting everything else downward if possible. Yeah, you can adjust a smaller bike upwards, but I wouldn't recommend it...for comfort sake.
Sorry for the Jamis side-track. I did enjoy the ride of the 520, but I came to the conclusion that I'd have to put too much money into it in order to "make it" the way I'd want...which didn't make it a good deal for me.