I wouldn't worry about melting.... However, system stability is what you should be concerned about.
The Celeron 2.0ghz will draw about 55w of power. With the notebook drive, this would work well with an Opus 150w. You might consider an M2ATX and/or DSATX for power just to be on the safe side. You could also underclock/undervolt the CPU a bit to gain some power savings. Realistically, I don't think you'd have a problem wither way.