Should I use Nvidia graphics card for sound

Hello all, may I pick your brains....

My Gigabyte Z68X-UD3-B3 has on board sound (azalia) The video card Asus GTX560 has on board (Nvidia) sound.

To minimise performance loss in P3D or FSX whilst using sound should I

a)   use on board sound and route through the video card to the HDM/DVII socket, or

b)   just use on board sound, or

c)   install separate sound blaster card (I have an old one spare) so not using cpu or gpu, or

d)   use the Asus graphics card for sound, or

e)   get a life and stop being OCD about FSX fps.

What I am asking is which is worse, to have a hit on the GPU or the CPU.  The GTX560 is only 1gb so struggles with P3D consequently mainly using FSX for now. (can't afford a Titan).

To round off - the cpu is a 2700K OC to 4.5mhz and 8mb ram with SSD storage. 

I would prefer to continue to use the DVI connection to the monitor speakers but will sacrifice this if a real performance increase is noted from the separate sound card option.

Thanks for any input.

Gordon

Don't know how the emoticon appeared !! Not supposed to be there.