Your 400W Sparkle should be able to handle that.
Right now I have a P3-700E @ 1085MHz on an ASUS P3V4X, 2 vid cards (1 pci), sound card, scsi card, cdrw, dvd, scsi cdrom, 4 IDE HD (3x7200RPM,1x5400RPM), and who knows how many fans fit into the Supermicro SC750A case. You should be fine.