At the very least, all these tax dollars should fund COMPETITIVE PRIZES, not contracts...
At the very least, Astrium's apparently failed Beagle 2 mission suggests that the same money could be better spent in the form of competitive prize offerings, NOT monopoly-anointing contracts:
http://www.SpaceProjects.com/prizes
Like you, I'm a huge fan of the human exploration and colonization to Mars. I think it should be funded by competitive prizes, though.