Not to ask a dumb question (as I don't know your level of computer skills, and you may have already checked this), but have you checked the volume settings on the sound output from your PC?
I don't know of any notebook audio cards having "line out" (non-amplified), so I would lean toward an external audio card that has either a coax or optical digital output.
A standard headphone audio output is subject to whatever you have the audio levels set at on the PC. Using an external audio card with a direct digital output, gives you a line level audio output, then puts the digital to analog conversion tasks onto your receiver, a D/A converter, I am guessing, with a bit more horsepower than the one on your Dell.
Check Creative Lab's USB Soundblaster Digital Music LX;
http://www.creative.com/products/product.asp?category=1&subcategory=207&product=10246
or, if you've got a spare PC card slot;
http://www.creative.com/products/product.asp?category=1&subcategory=204&product=10769
Good luck,
Spence
