I love WinUAE but if I am playing single disk based games I think Fellows is a better emulator. As for the Celeron...I love em.
My emu box has a native 1.8GHZ Celeron in it, however with some heavey cooling its running at a nice cool 2.4GHZ I did push it to 2.8 but it squeeled like a pig thats had its nuts chopped off and rolling around on its back with its ickle legs in the air. Couple that with a heafty dose of 750MB 333Mhz DDR RAM, a Geforce 4200TI Ultra and a BIG TV screen and you have one mean emu machine....Although I have to slow it down for some of the miggy stuff.