Hi Steve, it’s a tough call. The prices you see on sites such as usedlighting.com and gearsource are very tempting, but used moving lights are always a gamble, especially ones around the age that you’re looking to buy. Prisms aren’t hard to find, and neither is a good (enough) white. Neither of your criteria points scream to go buy old light fixtures. They WILL break down and they WILL need parts, attention, and TLC.
I still have some High End Studio Beams in inventory that are quickly reaching the 20 year old mark, and while I’ve maintained them with the intention of doing so until an LED fixture of equivalent output and color mixing quality is available (and they finally are), this isn’t a model I’d buy into today. Five to ten years ago it made sense in the right situation, but not now.
Some fixtures hold up better than others, but given the tremendous improvement in lighting instruments over the past decade there’s a reason why people are selling these dinosaurs for next to nothing.
My vote would be to strongly consider something at the upper end of the Chauvet Rogue Series. It’s not too far beyond the upper limit of your budget, and that’s money you’ll quickly save by not having to buy replacement parts for old lights. Trust me, that cost adds up quickly. You’ll also avoid having a reputation of using outdated equipment of questionable reliability, if that matters for anything. If you can’t afford even something like a Rogue series fixture, I’d suggest renting until you can. Otherwise, you’re just going to end up with fixtures in various states of disrepair that don’t make financial sense to continue maintaining.
Also, with these bigger lights you have to really pay attention to the power they need. Many can’t run on 120v power. Hope this helps!