Currently using a TC Electronics BG250 combo. Playing mostly weddings and similar gigs. 99% of the time I’m running through a pa. I’ve used this amp on larger gigs and outdoor and it worked ok with help from monitors. It was cranked a few times.
so now looking to get something with a bit more than the 250 watts I’m currently using. Leaning towards a class D head with a 2x10 or 4x10 cab. Do I need 800 watts or will 500 be enough of a step up?
I would suggest you go with the 800-watt amp because it will always be enough. Honestly the 500-watt should work fine most of the time, but the 800 watt amp will give you more headroom and will run cooler than the 500-watt amp would, while it's at it.
I have a couple of 800-watt amps. One is my big Eden amp that will do 400-watts into 4Ω per side and it has two power channels. It will also bridge those two power channels together and put out 800-watts rms into 8Ω. I've used that amp bridged at 800-watts since 2015 when I bought a DNS-410 cab by DNA That handles 1400-watts rms with a max SPL of 137db. My 800-watt amp can push that to a little over 134db.
Also used that with my DNS-210 which handles 700-watts rms and has a max SPL of 134db. I bought that one in 2019 when I was accepted to the DNA Endorser Program. Both are really loud cabinets that are super clear, clean, and articulate with a really solid and focused bottom end. I've ended up using that DNS-210 for all my indoor venues now, small to large, because it's so loud.
In 2021 I bought my DNA-800 class D amp that has a built in compressor with adjustable threshold and ratio controls. It only weighs 4.8-lbs, whereas my big Eden amp weighs about 36-lbs in its rack. It puts out 400-watts into 8Ω, 800-watts into 4Ω, and as the manual says, "almost full power" into 2Ω). So it only puts out 400-watts into either one of those cabs but will put out 800 if I ever need to stack them up and use both at the same time. Good news is that the 400-watts into my DNS-210 still puts out more than enough sound for all my indoor gigs because the cabs are so sensitive.
So, I'm an 800-watt guy. Was considering buying a 500-watt Eden TN-501, which has a really nice sound and versatile EQ, but it was $649 and for $150 more ($799) I could get the 800-watt amp. Plus the 800-watt amp (DNA-800) was even lighter than the Eden 500-watt one (TN-501), and quieter too because it doesn't even have a fan. The Eden TN-501 has a quiet fan that constantly runs.
I would highly suggest you get an 800-watt amp and two 210 8Ω cabs. The 400-watts or so will easily run one of the 210 cabs for small and medium indoor venues and if you play a large room than need more, you can add a second 210 cab so you'd have a de facto 800-watt, 410 set-up when you needed it for large venues, outdoor venues, or music festivals.