I've been using a Motorola SB6120 for over 7 years and never thought much about it. It's DOCSIS 3.0, everything worked and I can stream in 4K without any trouble. Our service is 100Mbps at $38/month after taxes.

Mrs Fife called them about an outage last weekend that lasted a few hours and when they followed up a couple of days later the person on the phone said that only 1 channel showed up on our cable modem from their end. It's supposed to be 4x4 so something isn't right. Maybe the lightning strike at our place in 2012 finally caught up with it.

Any advice for what to get? Our ISP rolled out DOCSIS 3.1 to our area earlier this year but we're not on a gigabit plan. I don't care if it has wifi, we already have a router that's pretty good.

That modem has reasonable logs & status page and I would check it first. If was in 1x mode would expect to see bad signal on channels and other indications. While its possible that you had a tech which was knows what direction is up, its far more likely that is one that uses that as the standard excuse.
I do recommend not integrating modem & router. Also docsis 3.1 is not a universal as 3.0. Lots of problems with specific chip sets with specific providers. Make sure on compatibility list and check on here for general known issues about firmware issues https://www.speedguide.net/broadband.php.
That modem while long in the tooth has been one of the reliable ones across many providers.

I have a 6190 that I've been happy with. If I were buying new, I'd get a SB8200 to try to be as future proof as possible assuming it was compatible with my provider.

Yeah I plan on checking it out this afternoon and will post whatever I see. I haven't found a decent manual for whatever setup screens it has, but it looks like it downloads up to 42.884Mbps per channel. If I see more than that on a speed test I can assume that it's not operating on a single one. Also I didn't realize until today that WOW! moved us up to 100Mbps. They're lazy when it comes to billing, I still have a 2012 6 month promo applied.

The cable modem has been otherwise rock solid. I set it up over 7 years ago and forgot about it. It's outlasted two wireless routers at this point and the lightning strike took out the LCD controller in the TV and the DVI port on the desktop that it was connected to. It's been long enough so that I'm not sure if the cable modem was on a surge protector or not but it also tripped several breakers.

I have a SB6141 that is sitting around. If it gets you where you need to be, I'll trade for beer or ammo?

It looks to be a few years newer than yours, per amazon.

At this point I'm still playing around with what we have. Yesterday evening I had a couple of minutes to spare and I was connected to 4 channels down / 3 up. Numbers looked ok but a speed test over wifi showed only 30 down/5 up. My plan is 100 down / ??? up so something's not right.

I'm going to try again sometime today plugged directly into the cable modem to try and figure out if it's a modem issue or something with the router. 5 minutes of googling suggested that when our plan was upgraded (it was 25/5 originally 7 years ago) sometimes the ISP needs to push an update to the actual modem. Is that really true?

edit: Same results wired directly into the cable modem. I guess the 4 channels we're getting right now are too congested to pull more than what I'm seeing. I wound up ordering a SB6183 (16x4) modem since they're on sale on Amazon and anything less is no longer recommended.

I had a Motorola SB6120 I personally owned and used with Comcast/Xfinity. Never had any issues with it. About 2-3 months ago, I started receiving mail and phone calls that the modem was no longer going to be supported for my speed/price tier or something along those lines.

Was going to get an Arris surfboard but some of the upper tier ones are either very expensive or have had firmware issues. Ended up getting a Netgear CM1000, and haven't had any issues yet. I should be future proofed for awhile.

I think most of the stuff is garbage from the companies trying to drum up sales through them...

Most modems within the past few years will all support 300mbps+.

Only in cases where people are paying for 650-1000mbps could I see a potential issue

Edit- just saw that it was 7 years old and is listed at 150mbps down...so yeah. Maybe if you eventually expect 200mbps as standard....

If the cable company is upgrading their system from DOCSIS 3.0 to 3.1 your existing modem may not work going forward because DOCSIS 3.1 has backwards compatibility issues. We just went through this with our cable company. They told me that we would not be able to provide our own modem for a few months after the upgrade because they are still working on the infrastructure to authorize customer modems. So far they are not charging me for the one they provided so I will just wait and see.

OP I just decided to use the provided modem from Spectrum so I have a spare 6190 now. I'll sell it to you for less than retail if you're interested. Only about a year old.