The Galaxy cards with the 6 pin may allow it. I have the MSI cards.
I can confirm that the:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814487024Stops at 100% TDP. However so far its mining stable at an offset of +110mh on the core with no issues and the max evga precision will allow you to go is 135. (havent tried over +110 yet)
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.