Which of the above should I buy?

I am looking at purchasing my first DSLR which will be used for general photography and motorsport.
I currently have a Minolta Dimage Z1, my first digital camera purchased mainly because of its 10x zoom lens. Previously I used a Minolta 355mm SLR with Tamron zoom lens, can't remember focal length.

Having spent some time on the web looking at reviews I short listed the above 3 cameras but am now stuck as too which one is most suitable.
I cannot afford an expensive 70-300 zoom lens so will probably go for the Sigma 70-300 and hope my manual focusing is as good as it was with the 35mm SLR

I'm not sure that 'live view' is a 'must have' from the various reviews it seems more like a 'flavour of the month' and I found using the LCD screen on the Z1 for shooting was not comfortable. From the 355mm days I am used to using the viewfinder.

I will be interested to hear peoples views. Thanks