Definately check the power supply compatibility with any new motherboard. I think that ECS board uses a generic ATX power supply connector but other boards may not. A 300watt power supply is considered by many to be a minimum spec for a modern system, and most computer geeks I know will go for at least a 300 watt power supply from a name brand supplier. I've had mixed results with Enermax... They make good power supplies that actually are capable of putting out their specified power (unlike many cheap power supplies), however their return policy depends on the retailer's policy and I DID have one Enermax power supply go poof.
At least the enermax didn't take out my mobo when it died, which is one other characteristic of a quality power supply.
I read an article (I think it was on Tom's Hardware Page
http://www.tomshardware.com) that compared power supply quality with weight. They found a linear correlation with the quality of power conversion and the weight of the power supply. Even a cheap no-name power supply was often very good if it weighed a lot. The article went on to explain that the components that make up a high quality power supply are heavy (mostly larger than necessary capacitors and heatsinks) and their test samples supported the theory quite well. Enermax power supplies are pretty heavy

Jerry Pournelle has been writing a column in Byte magazine for many years. He's about as mistake-prone as they come (his motto is that he does these stupid things with computers so his readers don't have to) and he relies on PC Power and Cooling power supplies almost exclusively. It seems like every year or so he gets a generic power supply, it fails and takes out some other bit of hardware when it blows, and he replaces it with a PC Power and Cooling power supply and swears he'll never use a generic power supply again. Sure enough, 2 years later he'll somehow end up with a generic power supply and it will eventually fail and again his readers are told that the pain and suffering isn't worth the cheaper power supply cost

Back to the subject, make sure your power supply is good enough to take the extra load of the newer cpus, whether it's an AMD or Intel chip. Some motherboards (Pentium 4 mostly but some Athlon boards also) need an extra 4-pin connector so check the power requirements before you buy.
One last unrelated item - Frys has a GF4-4200 (64 meg) for $89 after mail in rebates. This is a very good price. If they're out of stock, the price is good until Tuesday so check back for open-box returns because Frys usually just puts returns back on the shelf, so just because they're out of stock today might not mean they're out of stock tomorrow

Best buy had a similiar deal after Thanksgiving so check there too.