Do you have SATA I or II (1.5Gbps or 3.0 Gbps)?
Much debate has gone into WD vs. Seagate.
I like Seagate, and they have outperformed WD in some, if not most, benchmarks. Just look at the warranty difference, and avg. seek times/latency. Seagate wins.
You might try an online retailer! Microcenter or Newegg should beat Best Buy's prices. But then you have to wait for shipping. Wanting to stay local, try a local computer retailer.
AND make sure your motherboard supports 48-bit LBA, to use hard drives over 137GB in size. But most all motherboards built after January 2003 should support large HDD. Some require a BIOS update. But I think you are okay (e.g. 4 year old machine = 2006).