Fascinating tests Don & Stephen and it seems to demonstrate that quality glass is the most important factor. That makes seems to me when I think about it. After all, if the lens can not resolve the detail, it doesn't matter how many pixels the sensor has, it can't recover the missing information.
This reminds me of a test I read in a hi-fi magazine back in the mid 80s (I think). They took a nominal £1000 budget and put two systems together. In the first they spent ~equal amounts on turntable (remember those), amp and speakers selecting their 'editor’s choice' products at that price point. For the second they selected a Linn LP12 turntable costing almost £800 and spent £100 each on amp and speakers again selecting editor’s choice budget products. The aim was to test the perceived wisdom of equal budget expenditure, against the philosophy that if you had a top class turntable to extract the maximum information off the vinyl record, even with a budget amp and speakers, to see which would be the more involving musical experience.
For those of you who have heard, or heard of, the legendary LP12 I won’t have to tell you the result
So the motto seems to be don't compromise on your lenses, if budget is an issue compromise on the camera body, and upgrade your lenses before letting the marketing hype of more megapixels persuade you into upgrading the camera. Providing they are sharp, images off a 6/8mp sensor will easily make good A3 prints.