Here's the question. With a choice between the 300a vs. the 366a (Slot-1), which should I get? I have a place where I can get the 300a for $65 (Costa Rica) or $70 (Malaysia). The 366 runs about $80 bucks or so. I've heard that some 366's can get to the big 550, but that the success rate is fairly low. This is going into a brand new system, so the PCI devices *should* be able to handle a odd bus speed (I'm getting PC100 RAM).
As long as you get a quality SlotKet adaptor (MSI, Abit, Asus), you should have no problems. I would stay away from the Abit BE6, as I have heard about many nightmares with them (not holding voltages, etc.). Get an Abit BH6 v.1.1. It has all of the toys of the BH6, just without the semi-funcitonal ATA/66. Be sure to get rev 1.1, not 1.01, of the BH6, as they changed the clock generator to give you more bus speeds. You should also be sure to get a Celeron 366 PPGA Malay made in week 14 or later. Week 13 PPGA celeries are as bad as the early Slot-1 366s, but strangely, almost ALL of the PPGA week 14 366s will run 550 without problems (they changed something between week 13 and week 14).