Read up on the Sussex breed. The best winter layers are hatched in March so you're right on schedule. Sussex are curious, friendly, handle confinement well ( they are also great free rangers). They're historically noted for their fine winter laying. They were bred for this so the chicks could be raised early and be ready for the early Spring holiday feasts in England. They call it "Derby Day".
Sussex are also top quality meat birds. They are a dual purpose breed, good for eggs and meat.     
     Buy from a  breeder, not a hatchery.   Look for chicks out of robust, full-bodied parents. You want a broad back, deep chest. Nice full breastbone.  The head should be refined but not scrawny. There's a fine picture of  quality Sussex body type located here:
http://katherineplumer.com/closeups/poultry/SOP/LLightSussex.html
The closer you can come to quality body type, the better layer and meat bird will be your Sussex. In the Sussex breed, body structure is directly related to productive capabilities. There are several colors of Sussex, pick one you like. The breed lays a large light to medium brown egg. The Standard says hens at 7 lbs. and Coccks about 9 lbs. There's a reason why we should stay about 7 lbs. for the hen. Larger hens aren't as productive layers. Historically,  the best layers in the breed hover between 6-7 lbs.
 
The Sussex is a soft feathered, close feathered breed. That means the birds should have soft underfeathers but not as much as the fluffy Orpingtons. 
Hard feathered birds  like the Old English games, have feathers which lay very tightly  against their bodies with little volume of underfeathers.
Soft feathered birds which are
 loose-feathered, like the Orpingtons, have soft feathers with voluminous underfeathers which make the birds look "fluffy". The best way to describe proper feathering on the Sussex is that the feathers should conform to the silhouette of the bird...not too closely, but close enough that they aren't disturbed by a puff of wind blowing against the lay of the feathers. Sussex which look like a big fluffy marshmallow puff are incorrect.
Sussex have a rich literary history  widely available for free on the internet or in many published books and magazines which makes studying the breed much easier. 
 Best Regards,
 Karen Tewart
 Public Relations Director
 American Sussex Association.