If you're going Mut, find some daggers with the same speed. 1.8 is the numbers to look for. if you're looking into getting a good pair once you hit 70, i would suggest checking out the AH for two . you can pick one up for about 45-60 gold. these daggers lasted me until Kara. enchant them with Agi and you'll be Vagine-O-might. i wouldn't goose them up since you're going to replace them soon and especially in the WotLK.
for combat daggers, i would still use a Ced's Carver as my MH and farm Heroic MgT for the for your OH. you can't really beat this dagger unless you want to spend some badges for the (50). key thing in this spec is your OH speed. Combat Pot relies on a how fast your OH is. the faster the better. hope this helps.