Of the cameras you listed, I'd avoid the QTsi - very little in the way of control and the kit lens it came with was not one of Minolta's better efforts. It was more a light, small P&S with interchangeable lenses. The 7xi was a great camera; I used one as my main body for 15-16 years. The controls take some time to learn. The 28-105xi zoom was decent; a bit heavy, and the autozoom feature was weird at first. Didn't catch on and was dropped a few years later.

Of the "si" cameras I liked the XTsi best; the focusing was enhanced over the "xi" series somewhat. Same outstanding metering system. Can't remember much about the 600si other than it had more manual controls like dials rather than push buttons; probably a nice body, though. The lens offered with the 600si you showed would put me off, but I'm not big on massive 3rd party zooms.

As to the Minolta 50, I believe it was pretty low quality, as was its kit lens.

I played with a Maxxum 5 and agree it would be a wonderful choice.