I use an Icebreaker Beast 150 Apollo V T-Shirt as my base layer, and the Icebreaker 260 GT Quantum Hood as my midlayer. Both are really nice and comfortable and work well together. The t-shirt is light weight and doesn't get horrible and cold when sweaty. I sweat a lot, and hate it when I stop, cool down and my base layer feels horribly cold and wet. The Icebreaker still gets sweaty but feels much comfier when I stop. Just a word of note, the 'Ivory/White' colour of the 150 weight Icebreaker gear is more like a dirty grey and can get fairly see through when wet.
The hoody is even better and work really well. The hood fits nice and tight yet doesn't feel restrictive. A really nice piece of clothing. The only downside for me is the overall weight, which is quite high. Worth it for the comfort though.