I havent really ever used 12s to be honest. Always had 10s and my current NLs are in 8s. I know a lot of people like the 12s though and if I only could have one pair, I would give 12s a serious look.
I personally think Slik, Vanguard and Manfrotto all make affordable and good tripods. I personally like the flip locks but I am using a Slik 824 right now that has the twist locks. Carbon vs aluminum is up to you and how much you will be packing it. I like carbon because you can get a more solid tripod for the same weight as some of the smaller aluminum ones are.
Tripod heads. I know the least amount about these. A lot of people really like the Siuri VA5 but I have a Vanguard PH114V. I like the Vanguard but it does have its issues. One is that it gets really hard to pan when it gets cold and the second is when you lock it down, it will flex the head and move your binos a little from where they were looking. I bought it knowing this but it has the same plate as my window mount and I got tired of switching plates.
If you are not in a hurry, you get get a good tripod setup for 200-300 bucks. Watch for things to go on sale.
Give CameralandNY a call. They deal with this stuff everyday and I would imagine they can help you get something that will work and fit your budget. I also hear good things about the optics dude at Gohunt.