which GPU is best?

[orcanice]

ASUS R9280X-DC2-3GD5
or
Sapphire TOXIC R9 280X



and what motherboard + cpu + psu should i buy.

[crazyates]

ASUS R9280X-DC2-3GD5
or
Sapphire TOXIC R9 280X

and what motherboard + cpu + psu should i buy.

Here are the MB/CPU/RAM I used for 5x GPU for under $200, plus another $200 for a pair of 750W PSUs (which can run 5 undervolted 280xs).
https://bitcointalk.org/index.php?topic=7216.msg4380855#msg4380855

ASUS and Sapphire are both good brands, so I don't think you can go wrong with either one. I've heard those TOXIC 280x can reach upwards of 800KH/s, which is crazy good. However, that requires obscene overclocking and even overvolting, which I would avoid.

[orcanice]

if im going to get 3 or 4 280x how many watts should my PSU have?

[Gazza1]

if im going to get 3 or 4 280x how many watts should my PSU have?

850w minimum for 3, 950-1050w better
1200w-1300w for 4

[Pavlinius]

TOXIC would give you better performance and probably higher power consumption.

[crazyates]

TOXIC would give you better performance and probably higher power consumption.

And costs much more. Don't forget about that.