just a sugestion, if you want to start clean (new mobo and cpu and what not) , If you still want to stay economical, but still good for a small business, I recomend either a AMD Thunderbird (it has 256K of L2 Cache), or an Intel Coppermine P3 FCPGA (basically saying the socketed version).
now if you want to spend a little extra cash, and possible good investment for future usage (as we know, change is not always desirable) , you might want to look into the Xeon line of P3 , which are basically P3s, with anywhere from 512K to 4 megs of ondie cache, having more ondie cache is very useful for servers, where they're may be multiple user request, of course, I only recomend this if you plan on growing really fast.
Otherwise, something like a Tbird 1Ghtz , on say Asus KA7 (no audio) , is economical, and good (bout 200$ total just for the cpu and board) , but if you want something business wise (covers everything) , I belive the MSI K7T Master-SI is an ideal choice, a more expensive motherboard, but it carries almost everything, firewire, Ultra160 SCSI (very good for Server harddrives), etc, I just wish it had standard ATA/100 support as well, then you'd have all the bases covered.
Ok so enough with the hype rant, between your two chips, P3 would be my choice.
But if you do want recomendation on new hardware, just let us know what your goals are, that way you get something that suits your need, not something thats a monster (like that MSI board i recomended, or like that Xeon recomendation) you dont need. Karl Blessing aka kb244{fastHACK}