If Poly Hive weren't so polite he would post a link to this lol:
http://www.beekeepingforum.co.uk/showthread.php?t=14706
Really is the wrong time to buy bees; taking a hive through winter is frankly boring, and if you haven't monitored the colony through summer it could be difficult.
Starting with a nuc in spring is the perfect intro for a newbee. If you acquire from a good supplier, then you are guaranteed a good start, and having a smaller colony allows you to "ease into it". Furthermore, by the end of the summer, you should have a good strong colony, with a bit of honey to extract.
The fact that you say you can "feed all winter" suggests you are not ready. How many books have you read? Have you been to any classes? If you got the full colony, would you bee prepared for swarming in April? Handling in excess of 40,000 bees? OSR extraction?
A big colony can be very, very daunting for a newbee.
Control your excitement
, and do what's best for the bees: join your local assoc., wait till spring and then buy a well-sourced nuc.
Ben P