For pub gigs, unless spending a lot of money for the specific purpose of putting the whole band through the PA, usually the PA is vocals and possibly kick-drum (for a bit of presence). As such I`d agree, a 410 or 212 and a 500watt head will be plenty to handle the bass for the whole venue/audience. In general a 500watt head will put out 300/350watts at 8ohms so I`d be looking at an 8ohm 410 or 212 that is rated at 400watts or above.
Depending on sound required and budget there`s a great load of gear out there, Ashdown is my fave, and available for not much dosh if getting used gear. Similar is Hartke, Peavey, Laney, all be picked up for reasonable funds and all more than good enough for the job - I`ve toured all over the UK and a fair bit of Europe with my Ashdown gear and never had any issues at all.
Re the rigs through PAs, well unless the PA has very good monitoring, or you decide to go in ear monitoring, then your rig is still your on stage sound. Unless you can wholly trust the PA & monitors it`s nice to have a rig that is sufficient for the whole band to hear on stage.