Yes, 1000 STBs use IRDA, which most IR senders won't pass. There is at least one that will (DigiEye).
Another solution might be to use the
Red-Eye Translator which in conjunction with a cheap IR sender (wired or wireless) and an alternative remote, but this is also probably a bit of overkill.
It may sound silly, but have you considered making a hole in the cabinet...? Need not be an ugly hole - you can get plastic which is jet black in appearance but completely transparent to IR, and maybe you could incorporate a black 'decorative feature' in the door...