Well if there is no budget as you said does that mean you are willing to spend $1000+ or you are unclear how much you have/want to spend? If there truly is no budget then I would get a top of the line GPU however because your PSU is a little on the weaker side and you are going for medium level gaming I would go with a GeForce GT series card, (Not GTX series because of power limitations) not because of price, but because you are very limited by your power supply. If possible I would recommend upgrading to a higher wattage power supply so you can upgrade your system with a GeForce GTX series card rather than a GT series card.