Probably not quite that large, though I'm not sure. I think 35s are about the biggest I will be able to handle with the over-sized SKS chromoplastic fenders I have on, but it might be able to go up to 45. It looks like it has a lot of vertical clearance on the fork, presumably because they assume you'll be putting on fenders, but I don't know about width-wise. I'll keep you posted on how much room I have after I put the 35s on. My guess is that it could take up to 45s, but you'd need different rims. The wheelset is only so-so on the Aurora anyways.

550 is a great price if the cross check is lightly used, but do you really want flat bars if you're going on longer rides?