Hey! I'm new to the forum myself.
I'm new to bass gear entirely in fact, so take what I say with a grain of salt (possibly the whole salt shaker, actually! lol).
If I were you, I'd stay away from Peavey. I haven't read so far a single positive comment on any of their models. From what I can gather, they're reliable amps, but the tones they deliver leave a lot to be desired.
Ampeg on the other hand seems to be well liked, though some of their models appear to weigh a ton and reliability is mixed. I see some people having issues while other people have absolutely none.
Again, from my extremely limited experience, I see combos being cheaper than head+cab, but more limiting. Plus, if there's a problem with either the amp or speaker, you're screwed. Think of it as being the same thing as those VCR+TV deals that you sometimes see. If one of the 2 items breaks, you need to bring the entire device to get fixed, so you're without *both* of those things. If you have a problem with either a head or cab, you can simply use another one with the still-functioning other piece of equipment.
Remember my disclaimers.
Hopefully, you'll get some solid info from much more experienced and knowledgeable members than I.