Well good luck with that. Really your choices are very limited.
1.
http://www.newegg.com/Product/Product.asp?Item=N82E16813128017
Purple SATA ports are Raid 0/1 support from the JMicron chip. No listed on Newegg as supporting Raid but it does.
2.
http://www.newegg.com/Product/Product.asp?Item=N82E16813127005
P965 chipset has been overclocking very well so you should get good results with either board.
If you are willing to go open box. This 975 board also overclocks well.
1.
http://www.newegg.com/Product/Product.asp?Item=N82E16813130051R
2.
http://www.newegg.com/Product/Product.asp?Item=N82E16813131070R
P965 again but the sister board (non -E board) holds some world records) Including the one for E6400 using the Asus P5B Deluxe
Here is the link to the world records
http://www.xtreamsystems.org/forums/showthread.php?t=59753
You will see that in the Conroe range that 3 of the 5 records are held by the Asus p5b -deluxe. The other two are held by 975 boards.
One note you should look to change the ram to a higher speed rating. As you overclock you ram will over clock as well. With this ram you are good for 333mhz front side bus anything over this is a overclock of the ram. It maybe that the type of RAM you are ordering is known to over clock in to 1000 mhz range, in which case you are fine. If not then go for DDR2 800 instead as that gets you to 400 mhz without a problem and on Intel stock cooler you can easily do that (CPU would be at 8*400 or 3200 mhz which is a very nice overclock).
For SLI support there are hacked drivers that let you run SLI on 975 boards. Note if you go cross fire you can do that with the 965 chipset and see similar performace to 975 board. See Toms hardware for more information on this. I can not find the link now but I was sure I read a article on runing crossfire on 965 on Tom's Hardware. Maybe someone else has the link. Ok found it Not Tom's site but still http://www.firingsquad.com/hardware/ati_p965_crossfire_performance/
There are many other sites as well that cover this.
As far as I know the Nvidia 680i chipset overclocks well but it is out of your price range. Nvidia 500 series (for intel) does not overclock well at all so forget those.
Good luck to you.