I found a peavey blue voodoo head for $300 plus shipping I heard the heads are better than the combos is it worth it?
and how bad would it be if I used this cab with it I will probably upgrade the cab later

Or I could get the crate blue voodoo combo 2 12" for $300 with no shipping

what sgould I get
First off your link is broken .

You would get more sound out of the head and it will be better for when you start to play big venues, however the combo is much more practical and still will give a good sound.

The crates, i have heard, are amazing amps. Have a looksee at www.harmony-central.com/User_Reviews for more info on them both from people who have bought them.
Main Gear:

Santiago S3 Spanish Classical
PRS CE22 Mahogany
Mesa/Boogie F-50 combo w/ G12K-100
Teese RMC Wizard Wah
Rothwell Switchblade
Ibanez FL-9
Visual Sound Liquid Chorus V2