Hey2
The Celeron is socket 370 processor, the Duron and Athlon T-Birds are Socket A processors. The difference is also on the MOBO chipset, I am not well versed on Intel chipsets but I would imagine you would need to upgrade to get the most out of your new processor.
The Asus A7V is the MOBO I am using to build my new system. 4, count them FOUR IDE channels for up to 8 IDE/ATAPI devices, two channels ATA100, two channels ATA66/33. It is often compared to the ABIT K7, which has RAID onboard, but only two IDE channels. You can buy a 1 GHZ AMD T-Bird Athlon for around 250 bucks, and the MOBO's run between 130-150 bucks. The Celeron still runs on the 66mhz bus, which is ok but I wanna go faster. And DDR is just around the corner...
If you are into overclocking, the Celeron and Duron chips are an excellent choice, but spend the money and get a Quality board with the features you need first. The prices on MOBO's aren't as Volatile as the CPU market. And Anandtech has an proven record of solid product reviews, so start right here.