[Set]

Combinations are Hard Techniques that allow someone to purchase off the -6 penalty to the Rapid Strikes of a specific combo of Targeted Attacks. This is on Martial Arts, p.80

All-Out Grapple and Strike is a type of attack that allow you to, quite literally, Grapple and Strike. They are on Martial Arts, p.118 (I forgot to put them in the References, will update.)
When you do that, you get Double (One for a Grapple, one for an Attack) and if that Attack is thrusting, you get the benefits for All-Out Attack (Strong).

Maybe that wouldn't apply in this case since you aren't really pulling the guy's head to the point of your knife, but you may push him, both for the dagger to dig deeper, and for it to cut deeper (Tip Slash). So I think it does apply.

@EDIT: On the matter of approaching silently.

High-Tech, p.158 gives a table in which a "stalking person" (i.e. someone who has succeeded their Stealth roll) is 0.25 yard the "normal range of hearing". To perform the Combination I mentioned with full surprise would require you to be within your half-move range (you can move half your move when using an All-Out Attack), which is probably 2.5 or 3, something like that. This gives you 3 steps above the normal hearing of someone stalking (and you are stalking), so the guy would have -3 to hearing.

I'd say the most reasonable way to deal with Stealth rolls against someone who is alert, but not specifically searching for something RIGHT NOW (i.e. he is not taking Concentrate each turn to look for trouble) is: roll once a Quick Contest Stealth vs Hearing (unmodified). If Stealth wins, it's over. If Hearing wins or if there is a tie, note how much of a penalty you'd have to give Hearing for it to lose - that is the distance (in hearing steps) at which the Stealth guy will be noted.
Depending on the distance, Hearing guy might still be partially surprised. If Stealth guy has Combat Reflexes and a higher Speed, he can probably act on the moment he notices Hearing guy noticed him. Therefore, having him partially surprised.