Keep looking. It's worth it once you get one that is good.
If you have a bottle in your hands but haven't bought it yet, I found that a good indicator of quality is whether it has noticeable floating flakes in it. Hold it up to a light and take a look. Not haze, not particulates -- flakes. When a beer has that, I've found that it's gone off (some kind of oxidation, by taste). The beer will taste harsh, thin, and more bitter. I use that approach when looking at Westmalle Dubbel and DeKoninck with success too.
I've had maybe two dozen of these beers, and maybe a handful were that amazing quality. I had some back luck with buying the grey market beers in the US; those are mostly the ones that have been crap. Anyone go to my talk on Belgian Dark Strongs at the AHA Conference in Chicago? I had a case of that beer, and it had that problem. Bought it local in Chicago at Sam's (now Binny's).
It's a fragile beer.