The RR-888 is available at musicdirect.com for $685. I'd worry that the one on ebay is just a knock-off. At the full price, I'm pretty sure it will work wonders to my ears. At $39 from Amazon, I'd be less easily convinced.
OK, kidding aside, I did try the early RR-77 many years back. Thought I heard/felt a difference but who knows - may have just been expectation bias. I also got caught up in the Alan Maher tweaks and cyrstals as well. We've all tried lots of different things over the years. Like all tweaks - it never hurts to try. Just wish there was a UsedTweak.com site where I could flip some of the stuff I've accumulated over the years.