Should I buy a soundcard?

First of all my PC's motherboard is Intel D845PESV and my speakers are Creative Labs Cambridge SoundWorks PC Speaker System.I don't have any soundcard.I use the onboard soundcard of Intel D845PESV motherboard.I will upgrade my PC in a few months.I am thinking of getting Intel DG33FB motherboard.Intel DG33FB motherboard has onboard soundcard and supports High Definition Audio.My question is will the onboard soundcard of Intel DG33FB motherboard be better than soundcard's like Creative Sound Blaster X-Fi Extreme gamer,Creative Sound Blaster X-Fi Titanium,Creative Sound Blaster X-Fi Platinum,Creative Sound Blaster X-Fi Titanium Fatality Serires,Creative Sound Blaster X-Fi Platinum Fatality Serires etc or will be the same?Will my speakers be able to support the soundcard of Intel DG33FB motherboard and high definition audio?

I cant vouch for the onboard on Intel chipsets, but can confirm your speakers will work with it.

I must warn you: some games/setups HATE Creative sound cards, even under XP. My X-FI Xtremegamer has given me plenty of problems since I got it, so i'm now running off my onboard...all under XP 32 (and repeatable under Vista). I can not recommend getting a Creative card, as many people seem to get these issues with certain games. If you must buy a soundcard, I recommend looking elsewhere.