Alex...
You seem to be suggesting that this 'reduced footprint' is because of the stage space allotted you at certain venues..? If this is the case, would it not also be the case that these same venues are, themselves, somewhat small..? Following this 'logic' further, and still bearing in mind the acoustic duo nature of your band, I would think that the power put out by your present powered mixer (150-180W into one 8 Ohm speaker...) should suffice. Many decades ago I played drums with Porpoise, a light folk-rock group of buddies. Our set was heavily biased towards vocal rendition, but even with drums (played lightly, and damped...) a bass, electric guitar, acoustic guitar, mandolin and violin, we never had PA problems in small halls, clubs and such, using a 200w amp turned up to about 1 (of 10...). Later, in France, I've played weddings in restaurants and small halls with drums and accordion, with pretty small Montarbo PAs, about shoe-box sized. It's true that we couldn't have turned up to 'deafening' if we'd tried, but we never lacked volume, nor 'punch'. For bigger venues (normal pubs..?) you'd be using both speakers, anyway, but one Wharfedale will do the trick, I'd say, even with your current mixer/amp. Any louder and you'd be running into feedback issues, in any case, I reckon. I could be wrong, but without spending quite a lot more than the budget announced, I'd say you've already got the best you need.
I'd add that, in those heady times described above, there was no question of IEM, or even foldback at all..! We just listened to what was going on, that's all..!
Just my tuppence-worth; hope this helps.