I went to Niseko in Jan and booked through Deep Powder Tours
They were great, have an office in town and can organise a lot of additional stuff for you, the support we got from them was great.
skimax also have a few deals going and both of those web sites have some info to read that might help you pick a resort.
Niseko is a huge mountain with the deepest and most reliable powder youll find anywhere. Nightlife was quite tame and all bars/restaurants tend to be very small. If you want to party hard and pick up chicks then Niseko probably isnt the best choice. If you want waist (sometimes shoulder) deep powder, short lift ques and enough terrain to keep you occupied for weeks, then Niseko is a good choice.