Thanks to everyone for your input - I'm very grateful for the information.
However, I must say that I have miscalculated the sums - still not gotten used -to PLN, I suppose. Instead of 200 PLN, which would be ~50 EUR, my comfortable budget is twice that, `100 EUR (which would mean, I suppose, around 400 PLN), with an opportunity to throw about 20EUR (or about 80 PLN) on top. I've corrected the numbers in the first post.
This means that Benevento is well within what I'd be OK with paying, and I'd love to pull the trigger on those, although their measurement system seems a bit weird. I have the measurements for the pants I believe fit me quite well, but that for crotch to inseam, and the website takes those from hip to inseam. I think I'll be in touch with their customer service and hope we can figure a pair or two out for me.
Otherwise, has anyone had experience with Pierre Cardin? I've had an opportunity to try their "Lyon-fit" pants in a trip once, and felt very satisfied with the way they sat on me, but I'm not sure about the price-to-quality ratio.