I actually researched this same thing a couple years back for my father's 870. We were looking for a good quality red dot that would take the pounding of an 870 shooting 3" SST hornadys during deer season and not brake the bank. I do not recommend going too cheap on your red dot. You want to purchase one that is going to handle the recoil and still track well. After some research I settled on an Ultra-dot match dot. I purchased it thru Midwayusa. It was around 240 and I believe they still are. There is also an Ultra-dot for 189, It just doesn't have as many options with dot size. Dot size is usually 1moa, 2moa, 4moa. It just basically means, from my understanding and experience, how much of the target is covered up when aiming. Obviously smaller the dot more pinpoint the accuracy. I looked all over the web and these red dots get really good reviews on shotguns and handguns. Seems like they are popular with the match pistol crowd as well. We set it up on my fathers 870 and zeroed it at 50yds. It helped his grouping big time. We moved out to 100yds and played around shooting our steel 8" swingers and he could hit it all day long. Something he couldn't do with just his stock iron sights. His eye sight is getting worse so I figured a red dot would help him out and it did. No problem hitting an Illinois white tail. Not sure of course how they work patterning a Turkey or coyote load but they are great with slugs. Scope has stayed on track each season so far. Have not had to adjust it, just take it out of the safe and check zero. I also recommend having your 870 drilled and tapped for actual weaver style base mounts. We had that done for around 70 here and it came with the mounts. They seem more solid than other styles. I've had a lot of experience with aim-point and eotech red dots when I was in the military, I'd say the ultra-dot for the money is good quality. Just my opinion and advice. Hopefully others have some good advice to share on other brands or this.