Good choice, especially for indoor/studio use. The AB800 may not have the power to overcome the sun, limiting outdoor use. OTOH, the AB1600 may be a little too powerful for indoor use, and you're limited to 6-stops of adjustment. That's one reason I went with the Einstein 640 - as powerful as the AB1600, but the 9-stop range means it can be used easily indoors as well.
You should be very happy with the Paul C Buff AB800 heads. AB modifiers are absolute bargains so kit up. For others following this thread, Einsteins are the lighting market's worst kept secret. They are truly amazing. List price is less than a Canon 600EX-RT. http://www.paulcbuff.com/index.php
Just as a tryout I got two Paul C Buff Einsteins 18 months ago to see if they would pass the "tough-test" of constant location work. Six months in I was convinced and got another four. The Profoto Compact 600 monos were sold off and I'm now 100% Einstein except for the big Profoto floorpack in the studio. Just as useful as the full output is having the option to dial the Einsteins right down to 2.5 w/s. It's great when you want just a "wink" of light. On paper the Profoto and the Einstein have the same output, but my tests with standard reflectors gave the Einsteins a 1 stop advantage over the Profotos. This is not a raw output difference, it's efficient dish design. The Cyber Commander system allow you to have full control over 16 heads. Very cool.
Paul C Buff modifiers are so amazingly priced you'd think they missed out on a zero when you compare with Profoto or Broncolor. No, they're not in the same class in build quality, but for value and very light weight they can't be ignored. OMG the 86 inch parabolic reflector is under $100! I've been used to paying over $1000.