Your PSU is 450W, and that card required minimum 400W. That is 50W different which will lead your system become unstable. As far as I know, GTX 750 > GT 740. Since your requirements is medium gaming and high resolution, GTX 750 will do fine until you have enough money to move on to big brothers such as GTX 1070, GTX 1080, or GTX 980TI.
The GT 740 comes in three versions- Fermi, Kepler and Maxwell version. 450W is for the GT 740 that has a Fermi GPU. You're lucky to use ShadowPlay if you have a Kepler or Maxwell GPU
Are you saying that a 450W PSU is inadequate for a system when 400W is specified as the minimum? Seems unlikely. eVGA wants a minimum of 20A at +12V for the CPU that they recommend. I don't know which model of Thermaktake PSU "BunnyJ" has, but their Toughpower model is rated at 37A.
It may be worthwhile comparing the 750ti. It's a newer chipset (Maxwell instead of Kepler). I'm not sure that it's performance is much better than a GDD5 740, though.
Yes, it is inadequate for a system when 400W is specifed as the minimum. I wouldn't buy any graphics card if my PSU only have 50W left which can leads the system become unstable during gaming. Also, GTX 750 is a Maxwell architecture not Kepler architecture.
There is literary no major performance different going from 750 to 750TI. You're looking around 7% different, it like the same thing to AMD R9 280 and AMD R9 280X.
Well, I found a better card that only requires 350w min.
Amazon.com: EVGA GeForce GTX 950 2GB SC GAMING, Silent Cooling Graphics Card 02G-P4-2951-KR: Computers Accessories
Edit:
And I found this site where I computed an estimated power load:
OuterVision Power Supply Calculator
Using the basic version I get the following:
You can use pcpartspicker.com and enter all your components. It'l tell you if they're compatible with each other and what total wattage they're likely to use.
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