Thinking of getting another 285 board and sli my current set up. Does it make sense or should I just bite the bullet and spend 500 on a new video card. If so which board do you recommend? Another related question what advantage is 16x and 16x over 8x and 8x. Wondering if I should swap out the board while under 30 days. Currently have a Gigabyte GA-790XTA-UD4.
The x8/x8 offers a very slight performance penalty relative to x16/x16.
How much can you get another GTX 285 for? It's not really worth it if you can get it for around the same as an HD 5850. GTX 285 SLI is probably similar to HD 5850 CrossFireX, and that's around HD 5970 performance - however you have to take into account power consumption and the fact that it will not support DirectX 11.
GTX 285 sli should give you 5970-esque performance, so it should last you atleast for the next 2-3 years (considering only performance). Now the main factor is its lack of DX 11. But seeing that we still have new games that are compatible with DX 9, I suspect games coming out in even 2012-2013 would be Dx10 compatible.
So if you think you can live without DX11 eye-candy, another 285 would be worth it imo.