It is a dilemma, for sure... First point to note is that I'm still very much a noob fish-keeper and more or less at the beginning of the learning curve...
I definitely would like more flow and would like more surface agitation... Not 100% sure that I "need" more filtration, other than for the business of being unable to gravel vac significant areas of the substrate, leading to a fair old bit of detritus and the consequent experimentation with the Seachem Pristine etc...
I do have the APS Surface Skimmer filter, which is superb at what it does in fact and they are cheap as chips - but it's a bit too powerful from a flow point of view (350 l/h) and it's "fugly", as they say... Because it's a bit vicious, I don't run it all the time - which in itself is bothersome as it means inconsistent flow for the tank inhabitants...
So, I'm basically trying to navigate my way through and find the best all round solution to cover these various interlinked problems... The neatest solution would be the better canister filter, then the cheapest solution would be the small additional internal filter choice... That would still be a little intrusive, being in the tank, but infinitely more affordable...
I have considered wave makers, but they all tend to be a bit too powerful and start in that same ball park of flow as the surface skimmer... I have found, on eBay, a 150 l/h submersible pump that looks ok and is really quite small and is cheap - giving another option, although that's a bit too similar to the existing surface skimmer in terms of how to boost flow but wouldn't contribute in the same surface clearing way as the skimmer...
There doesn't appear to be an absolute "best" solution as such, so at the moment, all avenues are still potentially wide open...