Carved top mandolins are more expensive than flat top mandolins for comparable quality instruments. That being said, you do not have spend a significant amount for an upgrade, but you might have to do a little homework and think outside the box. Have you spent any time at
http://www.mandolincafe.com/ yet? It is a great forum with a phenomenal classified section.
My suggestion would be a used Gibson A-9. These are so good that I think Gibson literally stopped making them.
You might could swing an early 20's Gibson A Jr. Snakehead if you wanted to go the vintage route. They are oval hole, but most of them that I have played sound great.
I think that the Rigel A+ and even the A Natural are good values at around $1k. They don't really have a traditional bluegrass sound to them, and that makes them undervalued in the mandolin market.
Finally, you might be able to find a Bozeman made Flatiron A around $1000-$1200 if you are patient.