As head0001 said Knight and Thompson Center are the way to go. However, if you want to keep it under $500 I think the Triumph like a replied earlier is the way to go. Its the most advanced of them all and will run you about $450 on Cabelas if you order it. The encore and the knights are great, but are going to cost you more then your limit. There might be one knight or two Knights under $500. But i can tell you from experience the T/C Triumph is an amazing gun and your husband will be completely satisfied, not to mention its easy to shoot and clean, which is huge! If you read the reviews on cabelas there isnt a sole that doesnt like the T/C Triumph and with the weather sheild and the easy breach its hard to beat for that price.
Good luck