The problem is that sorting "nearest 1000" by date is pretty meaningless because, as you say, the "nearest 1000" radius changes every day.
For example, there could be a new cache today being the "newest" but it's sitting right on the edge of your PQ radius. Now if tomorrow two new caches are published closer, but the previous newest doesn't go down to place 3 in the "newest list" but drops out. Not really useful.
If you create, on the other hand, a PQ with say 50 miles distance, and then sort the results by date, you'll always see the newest caches within these 50 miles.
So I'd suggest 2 PQ for 2 different things:
- For the nearest caches in your area, use your PQ with 1000 caches from home coordinates.
- If you want to know the newest caches in your area, first decide how far you're interested in the newest caches, setup a PQ with that distance limit and then sort the results by date - you'll always see the newest caches on top even if there are more than 1000 caches.
Or you could just use GSAK (gsak.net) and put the PQs together and filter however you wish. That listing can certainly be sorted by date.
GSAK is great, but it doesn't have all the data for sorting yet - mainly FAV's aren't included in the GPX file.