This is something most of us 'modders' have been through. We are bombarded with Transporters sat on air, with rubber band stretched tyres fitted to very expensive wheels. We then take a look at our own vehicle and think they sit too high or doesn't look right.
First thing most do is try lowering springs, but this doesn't do anything except cost money we could of spent elsewhere. Then we go bigger wheels, often going straight for 20s. This then can make a Transporter look like it's on steroids. Yes, it fills the arch better with more wheel, but the van doesn't sit lower, it often looks like it's actually sitting higher. So then we spend more money on coilovers. Often the side effect of that is rubbing tyres on inner arch liners because we've just opted for the tyre suggested by the wheel supplier, which is often wrong in low situations.
It reads to me you are in the initial stages of this dilemma
@Jongall and walking down the same routes most people walk, which ends at a road that you still don't like, but by then you're skint or your wife has disowned you because they are throwing daft amounts of money at a van that in her words looked fine as it was.
You want it to look low or more of an even stance where everything flows and looks more proportioned, but you're happy with it's current comfort. Coilovers are potentially your only option, and there are several really good ones out there, not just Bilstein.
If you like your current wheels, you might find that getting the stance right, makes the wheels look right, saving you money on the 20s you think you might need. I always think Black wheels on a White vehicle works best, but i've concluded through expensive experience that Gloss Black wheels just don't work due to the shine of the tyre and inner arch liners. I find that you detail your wheel, and the tyre shine removes the definition between tyre and wheel. You don't detail the wheel and the lack of tyre shine against the Gloss Black wheel makes the tyres look awful, it's a no win situation that I haven't kept on my T6 for more than a week.
Yours might pop more if they were simply changed to a matt Black. The matt against the shine of the tyre and the the shine of the inner arches will pick out the wheel more, instead of it looking like one big clump of gloss Black.
@DaveyB picture proves that ethos. Less complex, different tone of Black and the wheel pops out more obvious. I've just had another set of wheels done by Duchy for my daughters Black Mini. She insisted she wanted Black wheels for the all Black look, but I told Jamie to do them matt. He persuaded me to try what he called 'Flat Black' it's not gloss and it's not Satin, it's an in-between. They look awesome on the Mini, and it works really well.
I know I waffle on about these things, but i've been there and spent more money than I should of done. I genuinely believe that if you get the stance right, the wheels work regardless on size for the simple reason that you set the suspension to the wheel you are wearing at that time. Try adjusting coilovers to fit 18" wheels, then whacking 20s on at that setting and you will soon see what I mean.