Yes, your power supply unit is okay, but NOT the very best, since it falls slightly under the lower TIER category on the PSU hierarchy list. It's an average quality unit by ANTEC, but it's not that bad either, IMO.
The actual AMP rating, depends on the exact Video Card model/brand, and manufacturer. Do the math. On your current PSU model, actually there are a pair of 12V rails.
Each are rated for 40A each, which gives a combined output of 62A or 744W. It's a multi-rail unit. So I think you should be fine, with your current power supply, if you are using the GTX 970 GPU, or some other GPU, unless you are facing some serious issues with your PSU under Heavy Gaming/load. In general, for most of the GTX 970 cards, the requirement is a minimum +12V current rating of 42A, but this also depends on the custom model as well.
On your current PSU/HCG-750M, there are 2 +12V rails, and so the total combined output rating will be 62A, or a total of 744W, which is enough, at least in my opinion.
Make a note though: The total wattage number of any PSU is not always really the most important deciding factor, primary concern is the 'quality' of power it produces, and the total capacity of the 12V source etc. Though how the rails are laid out does not affect that much, i.e. single/multiple +12V rail PSUs.
Multi-rail PSU can be mildly better, especially with high wattage units, but it won't have any impact on your performance. However, it can provide an extra layer of safety in case you get a short circuit. A multi-rail power supply has OCP on all +12V rails, ensuring that your PC components stay alive, if a problem like a short circuit occurs.
Hope this helps ?Are you facing any issues with this PSU ??