Just to let you know Realtek High definition audio is the default name that modern Windows computers name any sort of speaker. So in truth you have such standard stuff it's just the motherboard
. However do not frett, your new Headset will still work wonders, especially if you can get a proper amp with it. There are also some really nice sound cards available for really affordable prices take a look at this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16829132020
Now as for the headset you can pretty much go wild Corsair Vengeance 1500 and up, Sennheiser 350/360, Razer Tiamat/ Kraken Pro, Cavimanus GX, Astro A40's (A50's if you have a mad budget and want the best), Logitech G35, G430 (they are new), Steelseries Siberia V2.
Now after that list you really just need to pick a colour, shape and go to the store
They are all good/ the best