Peavey makes very good bass gear as they do PA gear, I have a bunch of both besides some other makes. You'll find some folks here don't like PV but to each their own, they're reliable and built like tanks and yes, you can get good tone but the beauty is in the ear of the beholder like anything else.
No real differences between 4-10s vs 1-15s intrinsically, it's a matter more of how the spkr cab was designed and what quality of drivers they put in there. That said, there are some sonic limitations w/each configuration, eg 2-10s generally not enough for a lot of larger/louder settings, 15s have some beaming issues w/the mids and highs, but like any engineering exercise, you have to make compromises. You will find excellent as well as excreable examples of every speaker configuration. So it's really a matter of what sounds good to you and what you're willing to schlep. And it depends on what kind of music you're going to be playing primarily. I know this sounds vague, but as you've no doubt learned from your guitar playing days you have to experiment and experience it yourself.
Check the FAQ sticky in the AMPS section of the bass guitar forum, very very helpful stuff in there.
Good luck and welcome to the deep end
