A while ago there was a Toms Hardware article dealing with this very issue.. Namely: Does it make a difference which chipset and which graphic cards are used together? The conclusion said there was no difference in any set up and I'll endeavour to find said article for you..
Edit: I hope this doesn't detract from your own studies here...
Yes I always believed it did not matter as well but the funny thing is I see plenty threads on issues with ATI cards and looking at specs of these people I notice that a common factor seemed to be running Intel and ATI together. I also can not find any proof to support this at all but it was just interesting so I thought lets just see what comes out of a poll like this.
I have personally had C2D+ATI 480, then upgraded to ATI 5870 - not a single issue. Maybe I should say I do indeed have faith in NVIDIA chips, they are great I think, but I should also note that there are quite a few threads related to problems with Intel+Nvidia.
I think many things effect games and graphics. It's just not down to what chipset your running or how good your graphics card is.. As I've mentioned before the amount of information that has to be processed is simply enormous and ANY weak link in the chain is going give out problems..
When building a gaming machine regardless of spec used each component should be read about and fully updated..
This is why gamers like cybercore or highwayman (even little old me) don't suffer from blue screens and the like. It's because they've updated their machines to the max and regularly keep them updated as well as clean..
I was running a NVIDIA 8800 GTS 512 and upgraded to the Radeon HD 5770 1GB and straight off I had major issues. Not even the manufacture could help solve these problems. Changed that card out for the NVIDIA GeForce GTX 470 issues gone. Granted the NVIDIA GeForce GTX 470 is a much more expensive card but as past experience with NVIDIA had shown me the same to be true, just plug in load software and never look back. After my issue I notice more and more threads about the ATI cards having similar if not the same problems I had. It always seemed to be the same fix a lot of tweaking changing drivers and just a huge amount of effort to sort it out. So my limited experience with ATI has made me an avid NVIDIA supporter
I agree that some components seem to work better with others and I'm at a loss to explain why you got such a bum rap with the 5770.. Being this side of the screen doesn't always make it easy when sorting other peoples problems but at least your now stable and gaming again.