Just a thought Emiliano,

Try using an old G5 with a RAM disk. If all you're running is a single output, it should work fine. I have a venue with 2 G5 Cats that are running HD with no problem.

For the cost, you could have G5 2 machines (primary and backup) so long as your volume of content isn't hugh.

Memory on a G5 is cheaper per Gb than Mtron.