I seem to be Tea at the moment. Oh well, so be it.
I'd have bought a K6-3/300, Cliptin. On 10th August 1998 our list price for a P-II 333 and board was A$1030. That was a VIA chipset baby AT board - the cheapest way to get into a P-II. But if you wanted something more-or less future-proof in a P-II board, then you probably wanted to go with a BX board - and they were dear. A P-II 333 with a BX board listed for $1230.
A K6-2/300 on an FIC VA-503+ listed for $690 - barely half the price of the P-II combo. Integer performance was superior (because of that 100MHz FSB that you didn't get in a P-II unless you shelled out an incredible $1450 for the P-II 350 - or just went stupid and bought a 450 for $2000 even.
Floating point performance was well down, of course, but people often forget that the AMD and Cyrix chips were able to multi-pipe a mixture of FP and integer instructions, which the Intel chips couldn't, and this made them better performers at a real-world mixture of FP and integer instructions than the benchmarks showed. (The Intel parts, on the other hand, while they couldn't do 1FP + 1INT instruction, could do 2 x FP. So it all depended on how many tasks you ran and what instruction mix you had.)
And on the other other hand, if you were into gaming, Intel didn't have any SIMD abilities then (unless you count the anemic MMX) whereas a lot of games supported 3DNow. In short, unless you had some very specific FP-heavy requirements, a K6-II/300 was equally useful and half the price.
As for the upgrade path from there, there were three main possibilities:
1: K6-II/300 and board for AU$690 Chip-upgrade to a K6-III/450 in August 1999 for $300 changeover: total cost: $990.
2: P-II 333 and VIA or LX board for $AU$1030 You've already blown your US$500 budget, so you can't upgrade it next year in 1999. If you find some cash do it anyway, you might have bought a K6-III/450 and board for $710 less about $150 trade-in, or about $550, or else you could have had a P-III 500 (the old, slow, external cache Katmai) for $1130 minus that same $150 trade-in.Best P-III board then was still the BX. Total cost either $1580 or about $2000.
3: P-II 333 and BX. Upgrade to a K6-III for $550, or chip-upgrade to a P-III/500 for $800. Total cost either $2000 or $2250.
Dualies I don't have pricing for. In fact, to this day, I have never sold a single dual CPU board. Not one. I did own a dual P-II 333 once, but I pulled the second CPU out and sold it because it didn't do anything under W98 (which is what that box was used for). Eventually I got tired of the poor performance of that Iwill LX-chipset-based P-II 333 and swapped it out for a K6-II/300, which killed it in every way. As a matter of interest, I still have the same main board in the same box (which lives in the workshop) but I gave it to Tannin who slipped in a K6-III+ and runs NT on it and uses it for burning CDs and folding proteins.
Oh, and I happen to own a dual ASUS Pentium Pro board. It has grown old and is no longer quite stable. (It's pretty close, but not quite). I did think about using it for my new FTP server and a little folding on the side, but I decided that the damn CPU fans were too loud to put up with and that I wanted to run either OS/2 or Linux on my server anyway. So it's sitting idle. Guess I'll just give it to Tannin for his collection.