Listen to the advice above.
Amp power ratings can be very misleading. A 1000W amp is only twice as loud as 100W into the same cab.
Speaker efficiency makes a huge difference, as does an amp with (good) built in compression/limiting.
That's why the above mentioned Trace Elliot Elf into an efficient cab can be as good as a 1000W combo with a crap speaker.
I used to gig with 150W and two 2x12 cabs in the 90s. These days a 500W Orange Terror into a single good 2x12 and it's difficult to set it quiet enough for most venues and I've used it ticking over in 250 capacity venues and open air gigs with no PA support. There's no upper limit (I saw the bass player of Preying Mantis use one in the Manchester O2, with PA support).
So my advice is choose an amp you like the sound of with power in the hundreds of watts and match it with a good (ideally the best you can afford) lightweight cab.
Amps are very personal as they determine your core sound.
Good cabs include GRBASS, LFsys, Barefaced, Markbass, TC Electronic.
The first two are a bit boutique. The other three probably cover 90% of the cabs I see used by regularly gigging bands.