KT7s and Durons can go to 1000 Mhz without the need to modify the mobo. If the Duron is locked then you have to close the L1 bridges. Of course, you need good cooling, both on the CPU and in the case. Remember, not all Durons can reach 1000 Mhz. (Mine will but I have to leave the case open).
It was my understanding that the Asus A7Vs, now being shipped, do no need modification either but you'll have to wait for an A7V owner to reply.
If you are talking about modifications to get 2.0 or more volts for the CPU Core, that is only required, sometimes, to overclock Thunderbirds, and usually well beyond 1000 Mhz.
If you need one of those mobos, I know that OCZ.SAFESHOPPER.COM sells modified KT7s and KT7-RAIDs (good to 2.2 volts). Price $139.99 and $164.99, respectively. They also sell pretested, overclocked processors and processor-mobo combinations. Their memory is very good.