Power Requirement Question- PCI-E 2.0 x16

[gpking]

I own an HP Pavilion (H8-1110) equipped with a GT520 (http://www.geforce.com/hardware/desktop-gpus/geforce-gt-520/specifications).
Since day one the graphics card has been the limiting factor here, so I am looking for some possible drop-in replacements to squeeze any extra performance out of this build.

This machine is equipped with a laughable 300W PSU, so external power to a card is not an option. I am limited to whatever the PCI-E 2.0 slot can put out.
I have read elsewhere online that said PCI slot can safely put out 60W, is this correct?
If I am limited to 60W, what is the best applicable Nvidia card that fits a PCI Express 2.0 x16?

Before anyone asks, no, I don't want to upgrade the PSU. Just swap graphics cards.

Thanks.

 

[AdviserKulikov]

GTX 750 Ti is the strongest card that fits without external power. (Some models require external power, get one of the smaller cards without extra PCI-e power connectors)

If you were living with a GT520 before, you'll love a 750Ti. No need for a PSU upgrade unless you suddenly decide you need shinier graphics than you are used to.

 

[Wolfshadw]

And just a point of reference, the PCI-Ex16 slot provides up to 75 watts of power. However, some proprietary motherboards have been known to limit that to just 25 watts.

-Wolf sends

 

[gpking]

@Wolfshadw & AdviserKulikov- Thank you both for your help.
Everywhere I read seemed to conclude a 300W PSU severely limited GPU choice (by not providing external power I guess?) Plus by my own ignorance I had no idea PCI-E 3.0 was backward compatible with 2.0 slots.

I'll price a 750Ti and some other cards and see which I like the best.

Thanks.