Hi,
What audio drivers have you installed? I'm using the onboard sound as well (analog) and i'm quite pleased with performance and sound quality. I'm using the Dreamax Cinema 6100 speakers (5.1). Maybe you should try different settings from NVidia Nforce control panel and from your speakers.
On the speakers setup sellect listening mode (Analog-Digital). I have "checked" the following boxes as well:
Create Center Channel, Center Channel 3D Pan, Create LFE channel and Rear speaker phase shift. Also, check your subwoofer's frequency respond and apply the maximum setting in Hz (with the bar) at LFE crossover frequency.
I'm using 3.66 UDF Nvidia Drivers, it's the best from all that i've tried.
Try playing with those settings first, the onboard sound of the NF7-S is quite good and the Soundstorm is a great feature!So i wouldn't advise you to spend extra money.
Abit NF7-S rev2.0 (nForce2-Ultra400)-(3.66 Nvidia drivers)
AMD Athlon XP 2400+@2600+ (12,5x166)
1GB-> 2X512MB Kingston RAM PC-3200 (DDR333)
Club3D Ati Radeon 9800 Pro 128MB (3,9 Catalyst)
Seagate Baracuda IV 60GB 7200Rpm-2MB Cache/Sata Connected Sil3112A-Serillel Adapter
Windows XP Pro with Service Pack 1