Will it really run without any issues?

Here's what happened.

My specs then:
CPU: AMD Phenom II X4 955 Black Edition
Mobo: MSI 770-C45
RAM: G.SKILL 4GB (2 x 2GB) 240-Pin SDRAM DDR3 1333 (PC3 10600)
GPU: NVidia GeForce GTX 470 (Galaxy)
PSU: Raidmax RX-850AE 850w ATX Power Supply 80 Plus Gold PSU

The GPU was new. So was the PSU. So I install both seemingly flawlessly and things are good. I have picture, I was able to game, all that good stuff. I always gamed after work so my computer was kept on at night until I went to bed.

Four days later, things went haywire. I leave my desk to take a phone call only to return 10-15 minutes later and my computer was turned off. Okay, wtf. So I attempt to turn it back on. A popping sound was made inside the tower. Computer turned on, only for the monitor to turn off about 30-60 seconds later while the computer itself still ran. Attempting to turn it off, I blew the circuit breaker. Yeah, I knew something was wrong.

I immediately suspected the PSU and the GPU. Maybe my wall sockets and surge protector couldn't handle that much power. I took out both PSU and GPU and put another in there. Both of lower power.

GPU: NVidia GeForce GTS 250 (PNY) (the GPU I had before I replaced it with the GTX 470)
PSU: Raidmax RX-630Z Smart Modular ATX Power Supply 630w (the PSU I had before I replaced it with the 850w)

It did the same thing. No popping sounds or circuits breaking, but the monitor could not maintain picture. I believed the motherboard's PCI-E x16 slot to be defective at this point so I replaced the motherboard. Here's what my specs look like right now:

CPU: AMD Phenom II X4 955 Black Edition
Mobo: MSI 870-G45
RAM: G.SKILL 4GB (2 x 2GB) 240-Pin SDRAM DDR3 1333 (PC3 10600)
GPU: NVidia GeForce GTS 250 (PNY)
PSU: Raidmax RX-630Z Smart Modular ATX Power Supply 630w

This was pretty much what I was running my system on previously and is currently running with absolutely no problems. I want to upgrade my GPU so I got a GTX 460. It requires the same wattage as the GTS 250 (450 watts).

My question is this: Can I install this card without ruining anything? Without circuits breaking? Without frying more motherboards? After what had happened with the 470, I've become paranoid. Especially so since it needs 2 of the 6-pin connectors. I consider myself to only be an amateur compared to many of you so I thought I'd come here before I junk any more parts...

Any and all advice would be appreciated. Thank you very much.