Sentey Power Supply Reliable?

The Sentey Metal Blade Power Series 750W (MBP750-HM) uses Sirtec as the OEM. Sirtec (a.k.a. High Power) is a decent OEM so there's nothing to worry about in terms of reliability.

It should be sufficient for most GeForce GTX 980 cards in 2-way SLI mode.

It wouldn't be sufficient for two Gigabyte GTX 980 G1 Gaming 4 GB [GV-N980G1 GAMING-4GD REV:1.0] cards in 2-way SLI though.