I'm very cheap and very poor but I wanted to know if I could expect any sort of performance increase if I replace my current gfx card and sound card (see "My PC" for those) with these off ebay:
NEW 8 Channel 8CH C-Media CMI8768 7.1 PCI Sound Card - eBay (item 360030718373 end time Mar-09-08 17:51:18 PDT)
GeForce 6200 256M AGP Graphics Card - eBay (item 330216334700 end time Mar-08-08 17:48:18 PST)

My speakers are:
Amazon.com: Altec Lansing AVS300 2.1 Computer Speakers (3-Speaker, White): Electronics
And Amazon.com: Altec Lansing OEM ACS21W 2 Piece Speaker System: Electronics
My monitor is: AccurateIT - 22" Mitsubishi VX1120 Diamondtron NF Microprocessor-based Monitor oem Gateway, 2048?1536, 0.24mm, Dual VGA, USB Hub **SALE**
None of which I plan on replacing, further more I do not do any gaming and the most graphics intensive thing I do is perhaps use Sierra Home Architect or watch Music Videos.

So, is it worth it to upgrade to the ones above?

They would help, yes. At least the graphics card would. I dont know about the soundcard. Onboard works just fine for me. You could also consider looking at this
Newegg.com - ASUS N7600GS SILENT/HTD/256M GeForce 7600GS 256MB 128-bit GDDR2 AGP 4X/8X Video Card - Retail
and this would also help
Newegg.com - CORSAIR ValueSelect 1GB 184-Pin DDR SDRAM DDR 400 (PC 3200) Desktop Memory - Retail