There are two types of bikes you could consider, a cross bike or a gravel bike, the differences that I know of is the gravel bike has a bit longer wheelbase, the head tube is taller, the head angle has more slack in it, the bottom bracket is a little bit lower, some can take all the way to a 55mm tire (depending on manufacture) but most tend to be around 45, this stuff makes the bike have a more relaxed ride then a cross bike which is more of a race bike that can only handle up to 35mm tires depending on the manufacture. Generally the cross bike will be a faster bike on pavement especially if you put 25 to 28mm smooth tires; but the gravel bike can go places the cross cannot, and it's wider tires will give you a more comfortable ride.
Also do you want to have fender and rack mounts just in case you ever decide to go bike camping, of course fender mounts could be used for any riding. If so then you need to find a bike that has those abilities.
For gravel the Fuji Jari 2.5 is a good bargain, not sure if any LBS's sell that brand any more but Performance Bicycle does at $700. The weak spot with this bike is the derailleurs and briftors, the Fuji uses Claris which isn't real good stuff BUT it will last awhile and to upgrade when a part wears out you can go a full three levels up to 105 and still won't be spending much but get a far better component.
Another great option for the price is the Diamondback Century which cost a tad more than the Fuji but only about $15 because it's on sale right now and Dicks Sporting Goods store should be able to bring one in for you to see. This bike has a one step up better transmission than the Fuji with using the Sora group, still you could at time of part failure upgrade two levels up to 105.
For cross bike you could look into the Nashbar alloy 105 cyclecross bike for just $849 and it already comes with the fantastic 105 transmission. Obviously this one is bit more then you said you wanted to spend, however if you keep your eye on it Nashbar will reduce that bike A LOT toward the end of the season or during on of their 20% off everything sales, they are currently limited in sizes but you could call them and see what size would fit you and then if they don't have your size ask when they will. This is the best I could find at this price point with a really good transmission.
