I can also confirm the EVGA FTW 750 Ti
http://www.newegg.com/Product/Product.aspx?Item=N82E16814487028also stops at 100TDP, and it has the 6-pin connector. It was overclocking nicely when actually in the motherboard, but now that it's on a powered riser, it doesn't seem to overclock nicely anymore. I can boost the clock and memory but the it has minimal effect on my hashrate, but strangely doesn't crash it either... Has anyone else seen this before with risers? I'll try a different one tomorrow, I bought a few different ones from various sources.
I've also received this card from nVidia as a review/test sample. still installing drivers for it....
Are you using a 1x to 16x powered riser? or a 16x to 16x unpowered one?