My parents still have a 2GHz Celeron with 512MB ram also. While I hate Celerons with a passion, it does them fine for emails and internet. Though my dad does get mad at it for being slow sometimes, even though it isn't actually as slow as he says... I also resell a lot of P3 and Celeron systems for people that need a PC and don't have a lot of money for a new one. If all they need it for is internet (as what most people use it for) they don't need anything amazing.
That being said, I will upgrade my P4 within the next few months hopefully, though it's not a largely needed upgrade, I'm big on having more power, so it will justify the cost. Just need to sell all my PCs in stock at the moment to buy it though...
As for the monitor subject, I want an Acer 19" widescreen, but am still debating on the Acer or another brand.
http://www.newegg.com/Product/Product.asp?item=N82E16824009091