Thanks for the help, kennah.
I believe I have found a compatible card that may be more feasible alternative for me, due to my current financial situation. If you (or someone else) could check to see if it is, in fact, a compatible upgrade, that would be great.
Here it is.
My "maximum bus setting" is PCI Express 2.0x16, according to the AMD Catalyst Control Center, so I searched for an upgrade based on those stipulations.
My computer specs, again, if anyone needs them:
Machine name: USER-6E7D75B11B
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 3 (2600.xpsp_sp3_qfe.101209-1646)
Language: English (Regional Setting: English)
System Manufacturer: HP-Pavilion
System Model: GS354AA-ABA a6203w
BIOS: Phoenix - AwardBIOS v6.00PG
Processor: AMD Athlon(tm) 64 X2 Dual Core Processor 4400+, MMX, 3DNow (2 CPUs), ~2.3GHz
Memory: 3070MB RAM
Page File: 832MB used, 3421MB available
Windows Dir: C:\WINDOWS
DirectX Version: DirectX 9.0c (4.09.0000.0904)
DX Setup Parameters: Not found
DxDiag Version: 5.03.2600.5512 32bit Unicode
Thanks again, GAF.
EDIT: If you could also give me a general estimate at the improvements I might see with this upgrade, that would be more than appreciated. I currently have a ATI Radeon HD 5450 PCI Express 2.0x16 1024MB DDR3