I would go with one of following 5' rear discharge mowers below. There are a lot more manufacturers out there, but this will give you a start. My personnel opinion, I think Woods has one of the best finishing mower on the market.
1. Woods PRD6000 (premium version)
2. Woods RDC60 (economy version)
3. Bushhog RDTH60
4. Rhino TM60 (premium version)
5. Rhino XM500 (economy version)
6. Landpride FDR1660
7. Befco C50-RD5H (premium version)
8. Befco C30-RD5H (economy version)