Have you tried a Fluval 404 yet? They are pretty solid compared to the 403. I only had 1 problem with it so far, but it was a biggie (and it was my fault). I went to put the top back on, but I had it on backwards (it was 2am). I went to lock the clamps in place and snapped one of htem in half!
Hagen sent me a replacement clamp right away thankfully, I didnt have to pay a cent!