You are ignoring that the HD4850 and HD4770 have very similar performance. The issue most definitely was not a CPU bottleneck if the HD4770 was "smooth" and the HD4850 was not. A cpu bottleneck doesn't make things less "smooth" anyway, it just means you wouldn't be able to use the card to its full potential which may be a waste of money. If your wife's computer had the same processor and hers could play those games smoothly while yours couldn't then most likely it was the lower settings alone that made the difference you saw or perhaps some other difference between the two systems. A more powerful video card will never make games less playable.
Like I said earlier what will be the bottleneck can change dramatically based on resolution and the game being played. This is a fact. You cant just say E7200 + HD4850 = bottleneck, it doesn't work like that. If you want to say in X game, at Y resolution processor Z will bottleneck card Q then fine. In this case the E6600 will actually bottleneck the HD4850(and any other capable card) in the more cpu intensive games although the high resolutions will make that less of an issue as the video card itself will often be stressed to give decent frame rates at a resolution higher than what is optimal for the card.
If you want to tell if the CPU is a bottleneck it can be tested by increasing the resolution. If the frames per second doesn't really go down much or stays the same then the processor is what is limiting frame rates.
As for the threads you linked the first seems to be saying the processor will bottleneck an HD4870 slightly which seems about right. The second is about the HD5870, a good bit more than twice as powerful as the HD4850 so it is simply irrelevant to this discussion. The third is about the HD4890 which is also a much more powerful card.