Choosing an SLR
Some of the smaller players produce competent camera bodies, the main problem is lack of lenses. While there's often a good selection from the manufacturer, there's often less available compared to Nikon or Canon.
A serious photographer makes a not insignificant investment in lenses (many times the cost of the camera body) and therefore you're stuck with that system unless you feel up to selling the whole lot and starting again.
I'd always recommend Canon or Nikon for this reason. Sony are making some headway too and with Fuji's SLRs you can use Nikon lenses anyway.