I play with a 6 piece band and I use an Ampeg BA210v2 combo (2 x10) 365w @ 8 ohms. With an Ampeg extension cab (also 2 x 10) it has 450w @ 8 ohms. It has a built in DI (Direct Connection to the PA using a mic cable (XLR)) which is nice if have room in your PA to support it. I'm pretty pleased with it, the Ampeg BAv2 and Rocket series have a "Scrambler" circuit that emulates the SWR grit. It works well. With an $600 - $800 budget you have some options, especially in the used market. I like the combo because it's all in one, for smaller gigs I use it standalone, for larger I add the 2 x 10 cab. Some folks prefer a head and cab combination, it's down to what works for you.
I think the majority are saying 500w would probably be a good starting point, and for metal that sounds right. FB market place sometimes has good deals, but I would also look into any used gear stores, this time of year most stores are trying to sell new gear - unfortunately music gear prices have gone up since COVID, hopefully heading back to normal. It won't hurt to find someone that knows bass gear (a bit anyway) to help you shop. It's important to make sure the gear you find is compatible, the power amp out is the impedance matching the speaker cabinet (with a combo it usually never an issue).
Going with a solid brand never hurts, Ampeg, Fender, GB, GK, Hartke, Peavey, etc... Just a word of warning with the Rumble 40... I loved the one I had, especially how light it was. When we had small practices I would bring it, as the volume got louder I'd push that little amp and eventually the speaker gave it up (luckily it was still under warranty). Those rare earth magnet speakers sound great and are super light, but IMO they can't take the abuse of regular spec'd out speakers. I exchanged it for an Ampeg BA115v2 (plus a few $$), which I leave in our practice studio, 5 years and going strong.
Good luck on finding a good setup,
Cheers
FYI: Bugera is made by Behringer... do a Google search on that model and see what the reviews say. In my experience, Behringer either works well, or is a poor product (not much in between). And you can't beat their prices...