I'm trying to get a new gpu aswell to help with the hash rate, don't know if I should get a 7950, a 280x or a 290, kind of tight on money right now and although it's an investiment with return so I don't know how should I handle this ..
Well, I have it working alongside my GTX 670 now.
The R9 280x provides nice bang for buck, but it runs pretty hot. It's fine though, as they can take the heat, but when it gets to max temp I drop from 700mhash/sec to 635mhash/sec, so realistically to get max performance I'll need to watercool it. It's a bit annoying that I bought the best performing/cheapest R9 280x that I could find, because I'll have to buy a Universal GPU waterblock to cool it now, as it's a non-reference board. Oh well. It'll still be way better than the stock air cooler. A decent 240 radiator should keep it running at 700mhash.
The water cooling should pay itself off over time via increased lifespan and possible overclocking, a little risky for long term use though.
http://www.scan.co.uk/products/3gb-msi-radeon-radeon-r9-280x-gaming-3g-28nm-6000mhz-gddr5-gpu-1000mhz-boost-1050mhz-2048-streams-hd
One of the cheapest 280X I have found and it is the MSI gaming version and can hash at 700-720 normal (no OC)
£240
Is that a fact, or based on posted performance? I ended up getting; http://www.scan.co.uk/products/3gb-xfx-radeon-r9-280x-boost-6000mhz-gddr5-gpu-850mhz-boost-1000mhz-dvi-hdmi-mdport-voltage-unlocked
Because it was the best I could find, myself.
I thought about that card but there isn't a water block for it (and they have no plan to make one) so I went for MSI just because it is cheaper than a few (not all) and I can water cool it, but this was before I found out about the universal watercooling bracket where you turn a CPU cooler i.e corsair H100 into a GPU cooler and a fan for the VRM
Yeah, it's a non-reference card, but you can put a Universal GPU block on it with some ramsinks. I wouldn't get a H100 myself. Not bad if you want an all-in-one, but I'd prefer a dedicated pump like a DDC.