Neither ECS or Shuttle would be my mfg of choice. They also probably won't provide any overclocking options.
Here's the advantages to the package I recommended. The CPU, a Mobile AMD 2500+, runs at lower voltage that the desktop model, it also has an unlocked multiplier, providing more overclocking flexibilty. The ABIT motherboard is very stable, and a known very good overclocker. It also has the nVidia chipset that offers very good audio performance, built-in networking, and many other nice features.
You might be thinking you don't want to mess with overclocking, but let me show you how easy it can be. Combine the CPU and mobo above with some PC3200 RAM, and simply set the FSB to 200mhz. This will give you 3200+ performance, without changing anything else (if you decide to "tweak" the settings, 3400+ speeds are very possible).