Sound Quality For PC Gaming

New to PC's ... wanting to build a gaming rig.  I Really want a good quality surround sound speaker system W/ superior Bass.  Wanted to know if i should buy a sound card or if the Motherboards on-board sound will suffice.  any reccomendations or specific product ideas? Also, What type of external Speaker Setup Should i have.  My Bottomline speaker is a 5.1 Digital Surround Sound System and my max budget for the speaker system would probably be around $300 give or take.  

Below, i have posted a link for my Motherboard...

http://www.newegg.com/Product/Product.aspx?Item=N82E16813128514&Tpk=Gigabyte%20GA-990FXA-UD3

Also, here's the link for a sound card that i have been looking at. WHAT DO U GUYS THINK, THIS SOUND CARD OR THE ON-BOARD AUDIO OF MY MOTHERBOARD.

http://us.store.creative.com/Creative-Sound-Blaster-Z-PCIe-Sound/M/B009ISU33E.htm

BTW, Here's the link for the speakers im considering.

http://www.logitech.com/en-us/product/surround-sound-speaker-z506?crid=47

Thx, 

Vic M

i have the gigabyte 108db via sound built into my UD3H and its pretty good, sure you could get better but my Z-5500's Play ball all day, if you want really good sound id say one of the first things to think of is the speakers themselves.

creative has some really good sound cards for not alot of money and even an inexpensive sound card is much much better then most onboard stuff and in terms of speakers i can recomend the logitec seround speakers and cant remeber the name but they have 5.1 speakers with really loud bass if you turn it up, the satelites sound REALLY  crisp too and they are only around 250 were i live, so would shop around for those 

Thx, Great Reccomendations.  i'll look into it