1. That system looks fine, mine is similar. my motherboard only has a 4x pcie connection for the other video card, so i had to run 2 PCs to run more than 2 monitors without it lagging.

2. My newly reformed heroic team is Prot pally, holy priest, destro lock, arcane mage (dual spec fire) and Ele shaman, who is replacing my second lock. I could see throwing a boomkin in the mix, my problem was gear, i had 4 clothies at one point, all looking for nearly the same stats. I sharded a ton of mail and leather caster gear. Emblems made up for a lot of the difference, but take a while to accumulate.

3. right on the money for that RAF. With an 80 lock, and an 80 priest healing the pet, you could probably boost up to 60, and probably up to 70. You can do 40-55 questing if you want to change it up, and go 55-65 in hellfire, then either try for Slave pens, or hit up Utgarde Keep. Once u get to 71, just farm AV. get some nice honor for your mains in the process. If you want tho, questing with RAF is so fast, i felt like i was cheating. I outleveled zones long before i was out of quests, so I just started doing the simple kill quests, and looked around for the group kill quests, and named miniboss kill quests, then moved on.

4. I kinda answered this in 3. But once u start RAF, think real hard about what classes and how many you want to play with, and get em all to 60 asap. I was late on my druids, and had to do some xfering around, and it ended up costing more had I just pushed through it and not wasted time.