SLI is ment for gaming. DFI is the best MOBO for those that Overclock. Don't spend the money for features that you don't intend to fully use.
When ever I get a new client that asks me to build them a custom PC the first question I always ask them is, "What do you intent on doing with it?" Then I recommend something that will only suite their needs and is futureproof.
Meh, DFI offers more than simply extended overclocking options and there are features worth paying for...for example CMOS reloaded is a godsend for anyone since you can tweak basically anything in the BIOS and revert back to older saved settings if you make a mistake or something...built in power and reset buttons are also nice for troubleshooting...good customer support is also something that is worth paying for
If you have the money a good motherboard will save many headaches in the future and increase the stability and reliability of your PC