I know where you're coming from. I find the cheaper K12 seats are more comfortable but still have 0 holding performance.
As an alternative if you have any DIY metalwork skills (or have a handy mate) then you can Mod other manufacturers seats to fit. I put some 207 seats in a Note without too much hassle and the seat belt buckles are compatible. I've also done a couple of seat conversions using BMW seats because I think they're dead comfy, they have a very flat mounting and you can "build" brackets to bolt into the car to fit the seats.
You loose the side airbags (which happens with buckets too) and remember to build strong because peak loading in a crash is about 60G.