RRR, I'm a newb so I don't have personal preferences yet. Given the blocks that are available now ('cause I'd like to be finished one day), the Tieton is the slimmest. It genuinely is a single slot with the backplate on it. The only other contender is the Aqua Computer block, but it doesn't have pass-through SLI fittings so... here we are.

If I had my choice of any manufacturer I suppose I'd chose EK or D-Tek. My D-Tek Fuzion v2 is very high quality.

AtlasShrugged