My MB has optical and coax on it. I will be using the logitech Z-5500 5.1 system or other speaker pkg with a optical hook up. So my question is will I get any benefit out of buying a high end sound card, or will it be a waste of money in my situation/setup?

Depends what your wanting to do. On my board, my board actually has HD sound output. Try it with onboard 1st, then if you don't like it, get the better card.

agreed. some onboard is fine, others stink. check yours out first with your speakers. if it sounds goods, leave it. if not, add in cards can make a huge difference.

Unless you are an audiophile you wont notice it. Onboard currently i believe doesnt support thinks like EAX and DDL so if you need those kind of features you will need an addon card.

IMHO, sound cards aren't worth it unless you work with audio files. I've found onboard sound to be hassle free, without driver issues found with Creative Labs products. EAX is a bit outdated and isn't as widely supported as it once was.

I do recommend people go for HD audio onboard when they upgrade. My son's 780G has better audio than my older 690V or my wife's 690G. With decent speakers, it makes a difference. CPU utilization isn't much of a problem anymore either. So just go for onboard sound if your board supports HD.