Congratulations! These are great systems! An 8600/300 is one of my daily vintage Macs for pretty much everything except for some programs I have which need a G3. I'll probably put 7.6.1 on it at some point and just have a 7/9 split.
I'm almost afraid to ask, but what speed did it start as, and do you have the original CPU? The 8600 and 9600 /250 and faster are unique among PCI power Macs for having the 604ev "Mach5" processor, which is a slightly update to the baseline 8600 and 9600 design, which itself is nearly identical to 8500 and 9500, which
itself is what many of the clones are based on. It's a great system either way, but if you got the original Mach5 CPU, I'd argue it's that much better, if only for the interest factor, because Mach5 didn't save the 8600 and 9600 from being absolutely curbstomped by the Power Macintosh G3 in performance.
So...i'll start this by saying i've wanted a 9600 for years. The last 6 slot mac and beige powerhouse before the G series took over.
Largely, I think the 9500 and 9600 are overrated. Six-slot PCI PowerMac builds are extremely boring to the point of being literally formulaic. There's a "here's how you build the best PowerMac 9600" post floating around here and some other vintage Mac web sites, and to be perfectly honest, the result of that is that you get a slow Power Macintosh G4 that's less good at running OS X, should the need arise.
That being said, keep the heat of the system in mind. There is a lot inside that machine that generates heat.
On the Mach5 (/250 and faster) 8600s, and I believe on the 9600s, there's a fairly large side fan. Does the /200 and/or this particular system not have that fan? I'd say that should keep things fine. It was designed with a bunch of '90s-era expansions, icnluding up to one full height 5.25-inch disk or two fast 3.5-inch disks at the bottom of the machine in mind. That, and, a G3 should run cooler than the 604e (even the ev) ever did.
(Although, I think it's largely a misnomer that the 604e/ev ever ran "hot" - keep in mind that what we think of as "hot" today is ~10-20x as hot as what was "hot" in the mid-late '90s, in office desktop computers. I suspect that the 604ev is probably a thoroughly bacon-frying 12-15 or so watts of TDP. G3s were known to be a bit less than that, if I'm remembering correctly.)
top off the RAM (why not?)
How much does it have?
Because system 7/8/9 doesn't use all that much, and because launching enough programs to make use of much more will reduce system stability outside of a few fairly niche workflows, none of which involve gaming in any way.
It can't hurt, but to completely fill even an 8600 (whose max ram is 768 megs, IIRC) is largely a point in maxing something out exclusively
because you can and not because it's a good idea.
Also maybe add the last two 1MB VRAM DIMMS? Would that help any other processing or will it have no impact if i'm using a video card?
Those will only impact the onboard video, so if you're not using it, then it won't help to add those additional pieces. I forget if there's any gotchas to using the a/v hardware with an add-in video card, so you might want to add the VRAM if you intend to do any video capture or output with it, which is absolutely one of the main things an 8500 or 8600 has over any 7000 series machine. (Other than the bigger case.)
Even then, it wouldn't really make anything faster, just make more video flows possible and make high color output on big/high resolution displays possible.
Would this one work?
