Audio distorted & ehcoe's

The audio is killing me here, I haven't been able to figure out what is the problem. The audio is somewhat distorted, and echoes a lot. I thought it was my crappy $10 walmart speakers, but I got some noise cancelling zune ear buds, and it sounds exactly the same. I'm not sure what to do. I thought maybe the audio drivers needs to be updated, but I've done that. Please help!

The hardware:
MOBO: ASUS P5Q Pro LGA 775 Intel P45 ATX Intel Motherboard

CPU: Intel Core 2 Duo E7300 Wolfdale 2.66GHz 3MB L2 Cache LGA 775 Dual-Core Processor

VIDEO: SAPPHIRE 100245L Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card

PSU & CASE: Antec Neo Power 500 500W ATX12V SLI Certified CrossFire Ready Modular Active PFC Power Supply

Antec Three Hundred Black Steel ATX Mid Tower Computer Case - Retail

RAM: CORSAIR 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory

HD: Western Digital Caviar SE WD1600AAJS 160GB 7200 RPM 8MB Cache SATA 3.0Gb/s Hard Drive