As a sound tech and musician, I've got both the desire to go for shock & awe and the pragmatism to keep things economical and portable. Across Canada there's all types of venues, some with full PA, half-assed PA, sometimes just a powered mixer and mains, sometimes none at all. It's a vast country with many large sparsely populated areas, so bringing PA along will always fill open dates on tour.
Keep in mind when you're playing a venue that has poor PA or no PA, the audience is expecting poor sound so you really don't have to aim all that high to make a good impression, and even then it won't improve turn-out until you've been through several times.
The solution I've worked out is to use my bass rig as part of the PA, serving as a "stage driver" which acts as vocal monitor, subwoofer, PA reinforcement, and of course bass amp. You have to be good with an EQ to ring it out since it's behind the vocal mics, but it's rather impressive what you can get out of it. It's no substitute for proper subwoofers and monitors, but far less expensive and space consuming, much better than just speakers on poles.
One trick I've worked out is to get the most kick out of a bass amp requires a subkick type mic, and what's worked well for me is a little practice bass amp with the back taken off. Wire the speaker to a patchcord (signal is high enough for line input) with +/- reversed (since the speaker is backwards). A normal kick mic produces a huge spike that's too much for a bass cab, but a subkick mic is more like a kick mic with a compressor on it, but with much better feedback rejection. It not only lets you get the most out of a bass cab but is also the best option considering the bass rig is generally close to the kick drum.
Considering we're only touring with modest PA speakers (Peavey PR12's) we definitely make a good impression wherever we run our own PA. Compared to hauling subs and monitors we're probably saving 30% on gas driving a smaller vehicle, not to mention our backs and setup/teardown time. We average over 300 miles a day on tour, and gas ain't cheap, especially where the population is sparse.