I'll echo most of what postrokfan said here. My front stage is currently comprised of B&W 600 Series speakers (685 for L/R, HTM61) powered by a Marantz AVR [SR5006]. The 3313 is a fairly powerful receiver, and will do well for the 683s - I have found that the 683s sound cleaner and more open with better amplification. The 600 Series centers don't get much love here or from reviewers, since they have off-axis dispersion problems. I"ve read here that the B&W 600 centers sound better placed vertically rather than horizontally, but have not the space required to test that out. If you're sitting directly in front of the center most of the time this won't be an issue. I almost bought a CM center instead, but since my room layout only allows for on-axis seating, the HTM61 works fine for me.
If you're going to get 600 series B&W floorstanders, I agree that the 683 is the way to go. They are better speakers overall than the 684. From my listening sessions with the 600 series towers, the 683s had a more defined midrange, better imaging, and less boated bass. In fact, I was originally going to get the 684. When I compared them to the 685, I found I liked the bookshelves better. The 684 sound like a slightly bloated, more bass-heavy 685 to me. After getting the 685, I was was also originally set on an HTM62 center and came away not liking it at all. It sounded weak, probably from the lower sensitivity, and lacked presence. Perhaps the FST midrange drivers in the 683 and HTM61 are what make them sound better.
As far as the dents go, to put it simply and for the sake of brevity: people are dumb. For whatever reason, they think expensive loudspeakers are meant to be poked and prodded and that the dust cap over the tweeter is some sort of button. Once they get to pushing in the tweeter, they get curious and start to push the drivers. This was a huge problem when Best Buy/Magnolia started carrying B&W product, and B&W reps came to install protectors for their tweeters (Fun side note: I had heard that people pushing in the tweeters were actually B&W fans angry at BB for starting to carry their product); If you have small children running around, it may be a problem, Otherwise I wouldn't worry about it. You can also keep the grilles on the speakers when not in use. In any case, the most commonly damaged part, the tweeter, like I mentioned is just the dust cap and shouldn't impact sound quality should it accidentally get pushed in.
While the 600 series are great speakers, I'd also advise that you try to find a Monitor Audio dealer in your area (http://www.monitoraudiousa.com/dealers
shows quite a few NY dealers), and give their Silver RX line a listen before committing to purchase anything. They occupy about the same price bracket as the 600 series and IMO offer a better value, not to mention more finish choices and exemplary build quality. To me, they were sonically closer to the CM range, definitely more refined and controlled than the 68x. I actually preferred the sound of the RX over the CM, I think. The RX center also sounded really good. Full disclosure: I recently purchased a pair of MA RX6 hat are going to replace my 685s. Doesn't hurt to check them out.
Whatever you end up doing, I wish you luck. Hope this post helped!