Xonar Essense STX Queries

These are my current specs:

 

Case: NZXT Phantom 410 - White

CPU: Intel Core i7 OC'd at 4.1ghz 

GPU's: Two GTX 670's in SLi

RAM: 8GB's DDR3 1333mhz ADATA Gaming series

Mobo: Z68 Asrock Extreme 4 Gen 3

CPU Cooler: Corsair Air Series A50 CPU Cooler

PSU: OCZ 850w Gold Certified

SSD: Crucial M4 256gb

HDD: 2TB thingiemajig

Steelseries 7H Headset

Steelseries Sensei Raw Mouse

Steelseries Qck Microfibre Mousepad

Logitech 5.1 Surround Sound System

 

Would a Xonar Essense STX make much difference to sound quality on my 7H's and Logitech surround sound system and do I have a beefy enough PSU to accomodate one?

the sound quality will be much better. and the power draw of the sound card is less than 15W, probably closer to 10W, so it should be just fine

Thanks Commissar.