@Ted
The numbers I used were purely hypothetical. My computer shipped with a 300W PSU, and I knew that wasn't gonna cut it for any kind of added GPU. After that, probably I would suggest doing some research on your machine if you're really going to pursue a mid-high range GPU. What Motherboard do you have, and how much power does it draw to feed the CPU & RAM you have?
Honestly though, if you're going to get a 900 series though, I highly recommend just trying to get a higher Watt Supply. Like I said, playing with under-powering things can really cause some bad juju (Up to and including burning out computer components). If you've had that 400W for less then 3 months theres a good chance you can take it back to wherever you got it from (Depends on the vendor, call and ask. Might need receipt, might not, some places can track card purchases of any sort including Debit, others can't or won't).
Also, IIRC the 145 Watt Draw it's talking about is its minimum draw. At times of heavy load or Graphics Boosting/Turbo is when it'll use the higher amounts. Nothing like getting everything hooked up, turn it on, get into a game, and 2 minutes in the computer powers down and the lights in the house go out cuz the circuit breaker flipped, with a nice smell of ozone permeating from your computer case..... (Absolute worst case scenario, highly unlikely to occur, but....).
@750ti
750ti is nothing to sneeze at. When it was released it became kind of the mid-range standard for many many games to be able to play decent on. I've never owned one so I can't speak directly about experiences with it..... But I've heard alot of good things. I would give pretty good odds it'd play TANE fairly well at lowest settings, and probably decent at mid settings depending on how resource intensive the Route/Rolling Stock are (Hinton Division seems to be kind of the Testing ground right now for people because of all the crazy high resource eating Speed Trees in it, and I would wager the 750Ti would probably struggle a bit with it with the rest of your set up, not sure though).
The real question is do you want to buy a 750ti and probably keep your current PSU, and replace them in a couple years? Or do you want to spend a bit more replace both PSU and GPU with a higher priced one and replace the pair probably 5+ down the line? I didn't buy the GTX970 because I want to play Battlefield-65 with super crazy ultra graphics where I can see the shadows of Blood Splatter through rippling water in the middle of a Windstorm.... I bought it because I fully expect it to meet my minimum needs for at least half a decade or so...... Of course, I paid a bit more then twice what the 750TI would have cost and dumped out for a $100 750 Watt supply at the same time, so did I really save money? /shrug, only time will tell..... But it runs TANE freakin awesome at least, lol.
-Falcus