actually the 1 gig Duron with the morgan core is around the same as a 1 gig tbird in performance. There are several reviews on it. For the extra few bucks, I would get the tbird over a duron. Both will need a good HSF to keep it cool and some case air circulation would not hurt either.
Pentium 3 1000 @ 1100 ( windows 2000 server), Abit bx-133, 256 Mb Mushkin Rev.3 cas 2-2-2, ATI Radeon
AMD Thunderbird 1.4 @ 1.63 (24/7) IWILL KK266R , Corsairs pc 150 cl2, Leadtek GeForce 3