ASUS M4A78-EM vs. ASUS M3A78-EM mobos

Hi I am looking for a mobo for HTPC build. I already have bought the AMD regor 250 processor. I was looking these two mobos at newegg.

Links.
ASUS M4A78-EM
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16813131324]
ASUS M3A78-EM [/url]

Asus websites says both mobos support AM3 chips. So is there any advantage to getting the M4A78? w/o the mail in rebate the price difference is only $7. So if its a better board in any way I'd get the M4A78.

As for memory when it says "DDR2 1066 is supported by AM2+/AM3 CPU for one DIMM per channel only" what does one DIMM per channel mean? Is it one memory stick per each dual channel? I guess the bottom line is I want to find out if I were to get AMD Regor 250 chip and one of the above mobos with 1066 memory (which is only $5 more that DDR800 memory) will that work well with this build? Thanks for your help.

Got the regor because building a HTPC. Decent performance for low power consumption. Much cheaper than Calisto. got it for $69.

any input on which mobo I should go with?

If you get a AM3 motherboard you will be able to use DDR3 memory as opposed to an AM2+(most support AM3 chips after bios flash) motherboard that will only support DDR2 memory. So in other words you are better off getting an AM3 board.