I'd like to upgrade the graphics card to something a bit more powerful, but the power supply is only 350W and there is no dedicated PCIe power cable (I'd have to use a molex adapter). The power supply is proprietary so not much chance of swapping it out for a bigger one.
There's a reasonably amount of room inside, so I could move to a dual slot card (although ideally a dual slot card that blows out the back) - the only really constraint is power.
What's the 'most powerful' card I could be looking at given my 350W limit? Could I get away with an AMD6850 even though in most cases a 450W power supply is recommended? What about adding another 5670 for crossfire? I think this is a possibility as I have 2x 16x slots on the motherboard, and it's stated to be crossfire compatible.
Any thoughts / recommendations gratefully received!
Antec is a good brand for PSUs so there's a good chance a 350w by them can handle up to an HD5770/6770. The link says its a custom PSU for that case specifically so I can't find info on the output of the +12v rail(s) which is the important rating. This info is usually on a chart on the side of the PSU. If you could check for such a chart and if it gives amperage or combined wattage for the +12v that would help determine what cards you can use.
The PSU needs to run the entire system, not just the video card. The max output on the +12v rails is what matters. The best card I would probably use on that PSU is the HD5770/6770. The HD6850 would probably work but it would be pushing thing to the limit which is never a good idea and can shorten the lifespan of the PSU as well as lower its efficiency. Seems like it might be difficult to replace as well. The HD5770/6770 will be a nice upgrade though. Almost twice as fast as your HD5670.