Well first of all the 300 or 400W tat u say shuld have PCIe connector, which will power the card...else there is no possiblity of using it...(mayb a convertor but not sure)
Next that powersupply shuld provide enuf power on the 12V rail to power the card...So its not possible to give a solution without more info about the powersupply...
Hmm...im quite positive il be able to hook it up to the card no problems...what risks will i be taking to test it out?
If you don't know say so please im not here for guesses and assumptions that could become a bit costly
Lolz its u who are making a guess work that u can hook up another PSU for the card...ppl will try to help only if u give more info...
And dont say am guessing/assuming tat too u giving so little info abt ur psu or specs...so dont expect ppl can give the correct suggestion then...
BUT! You would need to be able to power them both on at exactly the same time. So you could try split the signal from your motherboard to somehow switch on 2 PSU's - I dont know the way to do it as I know the power switch doesnt go straight to the PSU.
Your next problem is that unless you have 2 exact same PSU's they will both power up at slightly different times. This may cause a problem and the GFX card may not power up in time for the motherboard to detect that its on.
My opinion would be that it wouldn't work and would require you doing some fancy modifications to even get them to both switch on and provide power and the risk of damaging the motherboard, GFX and PSU's are high.
Ahhwell it was a shot in the dark...im not sure of the cables something about
This was the connector i was going on about...building pcs can't say i know much about but im sure its not that hard to grasp...im not about to head into anything risky without research and proper knowledge