You are thinking cheap , in first post, something to hold you over. Maybe think about a LG PA70G or some other LED PJ. Many of us picked them up for 399 on sale a while ago. Then in a few years get something else.
You wrote for indoor use it would only be 72 inch widescreen (6 foot screen), to 120 inch screen (10 foot outside), in dark environments.
The advantages of LED is 30,000 hours on unit compared to 2,000 hours for bulb if you went the JVC route and throwing away 300-400 dollars every 2,000 hours on bulb replacements (if you are lucky).
The LG pa70g comes with 2 year warranty, is small, portable, cheap, 6 watts of stereo speakers, 15,000:1 contrast ratio, 700 lumens. (Look at Redneck Geeks 41 minute YouTube video on it, and other videos on You tube.
You may or may not be sensitive to RBE effect on it, not many people report that problem with th pa70g, I don't notice it., so I don't know for you. But is your Rainbow Effect problem something you remember from the past , when tech level was in infancy or something you see on NEWER units?
I'm not saying you should buy an LED PJ, it might not work for you, but it is cheap with no worries about bulb replacement and would do a 72 inch screen in dark room or 120 inch in dark room. Something to research.
Now, if you are a videophile, maybe you need a JVC and 300 dollars every 2,000 hours is chicken feed , chump change, but for me, I'll take the LG PA70g at 399 dollars and enjoy 30,000 hours of watching , just like an HDTV. Also with LED PJ, you can turn it on and off anytime you want, can't do that with bulb based PJ. Every turn on and off of bulb uses 4 hours on bulb.
Quality Control on the LG LED's is something you might have to deal with, some early units had OUT OF BOX uniform focus issue, but , most people are reporting new build date units have better chance of getting focused unit. Just buy from place you can exchange or return without penalty.