I consider buying a 5970 and plug it into my present hardware. That is an ASUS P5N-E SLI, Miditower and 550W Power Supply.
Do you think that is possible?
I'm afraid there might be two problems: 1. Incompatible PCI-E Slot, 2. Too little power supply.
As an alternative, what would be the most efficient upgrade?
Another question: With my present hardware, videos aren't played fluently as soon as I launch poclbm-mod. Because I use that machine for everything, it would be important, that I can mine AND work at the same time. Is that possible? If not, I might reconsider the investment.
I appreciate any advice!
1) As long as it's a PCI-E x4 or better (which yours is then you're good). I'm mining on an Intel LGA 775 from the same era no problem.
2) 5970 uses almost 300 watts, 250 almost certainly enough for the rest of the system. You should definitely upgrade it if you're not going to use it as a dedicated miner.
Flash player, Firefox 4, Chrome, IE-9 and quite a few other apps are adding direct video support for rendering with opencl, the same interface you're using for mining. Using any program that accesses opencl is going to impact your mining speed. Flash player can be told not to use hardware rendering and will pass the load to your CPU. Some apps can't be told not to use it.