go to newegg they have several, it will only take u a few minutes to find them, as im a nice guy, ill give you a hint, in your options make sure you specify 6 ram slots....
I've seen one with 4 DDR2 slots and 2 DDR3 slots before. Is that what you're talking about because I mean both DDR2 and DDR3 in the same slot, if it's possible?
What mobos will support both DDR2 and DDR3 in the same slot?
None, because the keys are different between DDR2 and DDR3 modules, among other things. There are boards that have both types of slots, but that's not what you asked.