Looking for a recommendation on a backpack between 1700-1900 cubic inches that does NOT have a padded lap top area. What I want is a main compartment not split to take a computer with a second organizational pocket that would hold a Nexus 7 tablet.

Perhaps the Tom Bihn Synapse 25 might work, though the volume falls a bit below what you have specified. An 1800 cubic inch bag would be fairly large for a DAY pack. Is that the intended use?

Similar in size, less expensive, fewer outside pockets would be the Arcteryx Sebring 25, whose main compartment zipper seems positioned to promote a degree of urban area security.

Actually want to keep my rolling carry on at 19" vertical. Combination day pack and perhaps pack additional clothing if the bag gets too full

If you have a triathlon shop or specialty running store nearby, check out the Zoot bags. I saw these today and they were very lightweight and affordable.

http://www.amazon.com/Zoot-Sports-Performance-Transition-Bag/dp/B005LTR8TQ/ref=pd_sbs_a_2

http://www.amazon.com/Zoot-Sports-Performance-Sport-Transition/dp/B005LTR78S/ref=pd_sbs_a_4

I went by my local REI today and found myself UNIMPRESSED by the Arcteryx Sebring 25, which lacks any sort of waistbelt. For less money, the Mountain Hardwear Fluid 26 has a rather sophisticated waistbelt, and comes in two sizes for different torso lengths. BUT, I don't think there's a real substitute for going to a store like REI, Eastern Mountain Sports, etc. and checking these out directly, including trying them on with a typical load.