If you have a metal roof or solar panels/collectors, attic mounting will almost always give poor results.
But, because you intend to mount in your attic, I'll suggest the Winegard HD 7694P
http://www.solidsignal.com/pview.asp...0Antennas&sku=
This antenna enough gain to overcome the signal loss caused by wood and composite shingles. I have experience with attic mounted antennas... frustrating when it rains. Also this antenna is fairly big, if that's a problem then here is the next size smaller...
http://www.solidsignal.com/pview.asp...0Antennas&sku= This antenna would be fine outside on the roof but may be less than ideal in the attic.
Regardless of which antenna you choose, aim at about 85° per your compass, then adjust for the best indication on you signal meter.
I would expect you to see digital ABC, NBC, CBS, FOX, MyN, PBS as well as a few analog translators which may switch to digital in the future.
Regarding signal split: try running without an amplifier, just a passive splitter. If you need to add a distribution amplifier you can insert one later without much trouble. I own a PCT
http://www.solidsignal.com/pview.asp...mplifiers&sku= and recommend it
if you have a proven need. Adding an amplifier were one is not needed can actually cause problems.