If you are looking for a windows seedbox , there is not probably much option out there , but if you want a windows based seedbox the best for you is to go for following specifications on a dedocated server.
The specifications are as follows for the cheapest one that you can assemble on a dedicated server with all the installations done by you by the seedbox hosting company.
This is the cheapest windows seedbox you can get on a dedicated server installed and managed by the hosting company its important that you have to go for dedicated specifications because windows needs more RAM and also you would be using Windows Server Edition.