Socket 1366 - i7 930
it can be had for 200 at a Microcenter, about 215 after tax and shipping if you have someone in the states buy it for you.
Cant really say on a particular systemboard, havent had an intel system since the hyperthreaded P4s
A lot of people though have been doing good with EVGA boards, higher end MSI boards, a lot of Gigabyte and Asus boards.
If you are going to be using 3 GPUs, make sure you get a board with an NF200 chip depending on the GPU. It will split the lanes so you get full x16 lanes. Not really an issue unless you have 480s or more powerful in an x8 lane.
Socket AM3 - Phenom II 1055T
it can be had for 195 at a Microcenter, about 210 after tax and shipping if you have someone in the states buy it for you. OC'd it will run with an OC'd i7 930, mobos are cheaper as well. Would sstick to Asus, Gigabyte, & MSI boards.
890FX is the best of the chipsets that AMD has, if you want to use an Nvidia chipset, your board options are limited. You can still get 790FX boards, only difference, no SATA3 or USB3. If you get a 790FX, DFi boards are good boards as well, but the company is no longer making them but they will continune to service them. If you arent using multi GPU, then a 890X or an 880 board. Those chipsets will have fewer slots or else the same number of slots but fewer lanes per slot.
RAM:
A lot of people have been liking the newer G.Skill RAM, ECO and Trident. There is also your higher end more expensive Mushkin and Corsair RAM which will do while if you dont mind the money
Honestly though, my generic G.Skill RAM hasnt hindered any OC yet and it was only 105 for a 4gb kit. So you dont have to buy high end to get good ram